


^ 



V '' 



** / 





\* ... *** 



1 »°^ v 






;• ^ "V 



i 1 • ^ v -^. : 







vv 




so*? 1 - o V 



* ^ 



^ ** 
^ 








l-.^ 



^ V 













****** : - 
<, *'~rr«' ,g v "o '••»* a 










t&"- "^ 



^°* 



,;• 




^/ d> \ 






<, *'...' ,G V ^o 



o, 'o , . * A 



S 1 ' A V ^ ^ 




^ V 































JO 

y ... °^ • 































4.°^ 



"^ * 







G u * 



O.V- O 




•bv* 






iP^K V 

















c- 




^ /ate-, \/ 



■C. *'TT-* «G^ ^5, '».." A ^ *. ... 








P"*. 







i "^ " 



^0° 




^ o_ 


















4 t - . t> 







rr.* .6 






'/ <^ ** *. 











^1> 



,v^X l %^*.^% 



g 







o^ t .-V_. "*b 










j?-^ v 




;• ^ T 




i°v 





/^.-^ ^^^r^/ ^*^ T \^ % •.^r--^ V*--* 










,-- 






.6^ "o, -. . 7 • A 



./%. 



<> ^TT.'^ 






..7« A 











<> *'...' ,G 



* ^ 







y ... a ^ 



4 o*. 




,« -**A 



' <> 




^ v 






















G° / 







<» *'T7i' ^6 



3 *° «!» °^ 







:.^.„ 



o V 






•^o^ 



G w * 



*bv* 



-^o 



o V 















• ct5AW»k . o 



J£J 8823 



Bureau of Mines Information Circular/1980 



c-sty 



Surface Coal Mining Reclamation 
Equipment and Techniques 

Proceedings: Bureau of Mines Technology 
Transfer Seminars, Evansville, Ind., June 3, 1980, 
and Denver, Colo., June 5, 1980 

Compiled by Staff— U.S. Bureau of Mines 



<v@S 



UNITED STATES DEPARTMENT OF THE INTERIOR 



ll 

Information Circular 8823 

Surface Coal Mining Reclamation 
Equipment and Techniques 

Proceedings: Bureau of Mines Technology 
Transfer Seminars, Evansville, Ind., June 3, 1980, 
and Denver, Colo., June 5, 1980 

Compiled by Staff— U.S. Bureau of Mines 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Cecil D. Andrus, Secretary 

BUREAU OF MINES 

Lindsay D. Norman, Acting Director 




>c 






This publication has been cataloged as follows: 



Bureau of Mines Technology Transfer Seminars, Evansville, 
Ind., and Denver, Colo., 1980 

Surface coal mining reclamation equipment and techniques. 

(Information circular - Bureau of Mines ; 8823) 

Supt. of Docs, no.: I 28.27:8823. 

1. Coal mines and mining — Environmental aspects— Congresses. 2. 
Strip mining — Environmental aspects— Congresses. 3- Reclamation of 
land— Congresses. I. United States. Bureau of Mines. II. Title. III. 
Series' United States. Bureau of Mines. Information circular ; 8823. 



T-N-23SJJ4 [TD195.C58] 622s [631.6'4] 80-607057 



CONTENTS 

o _ 

Page 

^& 
-<? 

Abstract . . 1 

C: Introduction 1 

^ Reducing costs for recontouring mined land, by John M. Goris 2 

Design considerations of terrace-pit mining, by Gregory G. filler 22 

Topsoil rock removal, by T. M. Brady, W. W. Kaufman, and D. N. Reynold.. 30 
Transplanting native vegetation, by Earl M. Frizzell, James L. Smith, 

and Kent A. Crofts 48 

Selective overburden placement, by Gregory G. Miller 54 

Premining hydrologic conditions of five southeastern Ohio watersheds, 

by Gary E. Mcintosh 60 

Dragline cable removal safety techniques, by G. Ken Derby 74 









-i 



SURFACE COAL MINING RECLAMATION EQUIPMENT AND TECHNIQUES 

Proceedings: Bureau of Mines Technology Transfer Seminars, Evansville, Ind., 
June 3, 1980, and Denver, Colo., June 5, 1980 

Compiled by Staff-U.S. Bureau of Mines 



ABSTRACT 

These proceedings consist of papers presented at two Bureau of Mines 
Technology Transfer Seminars in early 1980 for the purpose of disseminating 
recent advances in mining technology related to surface coal mining reclamation. 

INTRODUCTION 

The Nation has a need for a safe, clean environment. Recognizing this 
fact, Congress has passed a wide variety of legislation in the last decade 
aimed at eliminating or reducing adverse impacts on the natural environment. 

Compliance with these environmental requirements has been difficult for 
the minerals industry. In some cases, technologies have not been available to 
adequately address the adverse environmental impacts of mining activities. In 
other cases, although technology is available, its installation and operation 
have imposed serious economic costs which the industry has found difficult or 
impossible to meet. These added expenses result in increased costs for domes- 
tic fuels and minerals, while curtailment of mining results in even greater 
dependence on foreign supply. In either case, attendant U.S. economic and 
national security problems are heightened. 

The Bureau of Mines Minerals Environmental Technology Program is struc- 
tured to address these impacts by developing cost-effective technology to 
remove or relieve constraints on domestic mineral production while at the same 
time protecting our environment. These proceedings consist of papers pre- 
sented at two Bureau of Mines Technology Transfer Seminars in early 1980 for 
the purpose of disseminating recent advances in technology related to mined- 
land reclamation. The goal of this subprogram is to improve postmining land 
use. Specific objectives of the research projects are to develop new tech- 
nology and better methods for — 

1. Contour restoration. 

2. Segregation, storage, and replacement of topsoil. 

3. Enhancing and sustaining vegetative cover. 

4. Preventing and treating postmining hazards through toxic material 
isolation and selective overburden handling. 



REDUCING COSTS FOR RECONTOURING MINED LAND 

by 

John M. Goris 



INTRODUCTION 

The need to develop better equipment and techniques for mine spoil level- 
ing is evident to people associated with the mining industry. Prior to the 
enactment of present reclamation laws, land restoration had little or no 
effect on production. Today, however, land restoration has become an integral 
part of mining, and problems associated with this activity not only can 
adversely affect production but can result in a shutdown of operations. The 
end result could be reduced coal production and extensive cost increases 
unless improved equipment and techniques are developed and utilized. 

The mining industry's response to the recontouring requirements has been 
to rely on available equipment such as tractor dozers, scrapers, graders, and 
in some instances draglines to meet recontouring needs. This can be an expen- 
sive compromise for many operations since recontouring conditions cover a very 
broad range, usually exceeding the equipment's range of efficient operation. 
For example, spoil material relocation distances can range from as little as 
20 feet to over 500 feet, whereas the effective range of a tractor dozer is 
approximately 100 feet, as seen in figure 1, which represents a typical pro- 
duction rate curve. Past this point, production rates are low and the cost 
per cubic yard of material moved increases. Therefore, total reliance on con- 
ventional tractor dozers for recontouring can be very expensive. 

Scrapers and draglines also have limitations. Several experimental sys- 
tems such as a winch-drawn blade system (fig. 2) are being researched by the 
Bureau of Mines; this system consists of two crescent-shaped buckets back-to- 
back and drawn perpendicular to the spoil bank by a winch and tailblock assem- 
bly. A prototype system has been field-tested, but it could be years before 
it is perfected and accepted by the industry. Even with this system, the mine 
operator will have to sacrifice the flexibility and mobility associated with 
tractor dozers. There are techniques available now, however, for improving 
the efficiency of tractor dozers that will result in more production at lower 
costs and lower fuel consumption. The same is also true for draglines 
employed in recontouring work. Following is a discussion of three specific 
areas of improvements for existing equipment that could reduce operating costs: 

1. Specialized blades for tractor dozers. 

2. Bulldozer work rate indicator. 

3. Backfilling final highwalls with draglines. 



Research civil engineer, Spokane Research Center, Bureau of Mines, 
Spokane, Wash. 




o 
o 



o 






o 






rO 




CO 
N 

o 

o 






u 




CD 


o 




CD 


£ 




**— 






- 


r 




Ld 


CI 




O 






-z. 


T 


O 


< 


n 


u 


\- 




CVJ 


co 


> 




o 


U 




X 


c 




CO 


o 




Z> 


I) 




Q. 


3 

o 



LU 
O 



o 


o 


O 


O 


o 


o 


o 


o 


O 


o 


■n. 


o 


1X5 


O 


m 


CVJ 


CVJ 


— 


— 





jm/£ p* '3ivcd Nouonaodd 



WINCH DOZER 




FIGURE 2. - Winch-drawn blade system. 

SPECIALIZED BLADES FOR TRACTOR DOZERS 



As part of the analysis of improving tractor dozer performance, it might 
be best to first review the requirements of leveling and recontouring area- 
mined land. Figure 3 shows a typical cross section of a uniform spoil bank. 
Tractor dozers begin leveling these banks by first pushing the peaks short dis- 
tances into adjacent valleys. As the work progresses, the spoil bank height 
decreases and the average push distance increases. For normal spoil banks the 
maximum distance may never exceed 150 feet. The final work is to grade the 
land and prepare it for planting. The same process is generally applied for 
leveling box-cut spoil except that push distances can reach 500 feet or more. 
These are poor working conditions for conventional tractor dozers. 




■Valley centerline to valley 
center line 



Note: 0.7X equals the weighted average 
distance from centerline to repose 
slope through a vertical cut of 
Y feet. 

FIGURE 3. - Typical cross section of a uniform spoil bank. 

The bank cubic yards (BCY) of material that must be moved depend primar- 
ily on the type of spoil bank (normal or box cut) , the crest-to-crest distance 
of the banks, the angle of repose, and the amount of rehandle. Table 1 shows 
the quantities of spoil material that must be handled in normal spoil as 
these conditions change. In comparison, it was determined in an extensive 
field project on leveling spoil banks (discussed later) that an average of 
27,901 BCY was handled per acre in leveling 275.9 acres of box-cut spoil. The 
average for normal 120-foot spoil on this project was 10,073 BCY. Therefore, 
the average ratio between the material handled in box-cut spoil and that moved 
in normal spoil was 2.77. 

TABLE 1. - Theoretical estimate of spoil material handled in normal spoil 







Bank cubic yards 


moved per 


acre 




Crest-to-crest 


Angle 


of repose = 


= 30° 


Angle 


of repose = 


= 36° 


distance, ft 


Rehandle 
pet 


Rehandle 
25 pet 


Rehandle 
40 pet 


Rehandle 
pet 


Rehandle 
25 pet 


Rehandle 
40 pet 


90 

120 


5,239 
6,593 


6,549 
8,241 


7,335 
9,230 


6,986 
8,791 


8,732 
10,989 


9,780 
12,307 



Next, consider an average dozing cycle in leveling spoil. Figure 4 shows 
the three primary phases, loading the blade, transferring (drifting) the mate- 
rial, and returning. At an average push distance of about 125 feet, the dozer 
will spend approximately 20 percent of its time filling the blade, 53 percent 
drifting the material, and 27 percent returning. Under good working condi- 
tions the production rate will be approximately 850 cubic yards per hour for a 




Cutting area 



Loading 



20% of time 



Drifting area 



Drifting 




53% of time 



Returning 




27% of time 
FIGURE 4. - Three primary phases of a dozing cycle. 



tractor dozer with about 400 horsepower and using a U-blade. 
conditions that affect this production rate follow: 



The primary job 



1. Push distance. 

2 . Grade . 

3. Type of material. 

4. Operator skill. 



5. Type of blade. 

6. Type of dozing. 

7. Job efficiency. 

8. Visibility. 



Each of these has some influence on production. Table 2 shows the range of 
correction factors applied to the production rate for most of the above job 
conditions as recommended by a major equipment manufacturer. These factors 
are multiplied by the production rates for optimum conditions, which are given 
in manufacturers' handbooks. It is obvious that all are significant if varied 
from one extreme to the next. The question is, which ones can you change and 
control to your advantage? Work at the Spokane Research Center has focused on 
four to date: push distance, type of blades, type of dozing conditions, and 
operator skills. 



TABLE 2. - Job conditions and correction factors for tractor dozer 



Job conditions 



production rates 
Correction factors Job conditions Correction factors 



Type of blade: 













.50-0. 


75 


Coal U-blade 




1.20 




Bowl (stockpiler) 




1.30 




Type of dozing: 








Slot 




1.20 






1 


.15-1. 


25 


Job efficiency: 












0.84 








0.67 




Visibility: 








Darknes s , ra in , 








snow, fog, or 












0.80 





Push distance Refer to manufac- 
turers' curves. 
Grade: 

Uphill (20 pet).. 0.65 

Uphill (10 pet).. 0.95 

Level (0 pet) 1.00 

Downhill (10 pet) 1.15 

Downhill (20 pet) 1.22 
Type of material: 

Loose stockpile.. 1.20 

Hard to cut 0.60-0.80 

Rock 0.60-0.80 

Operator skill: 

Excellent 1.00 

Average 0.75 

Poor 0.60 

Push Distance, Type of Blades and Type of Dozing 

The first three factors are actually interrelated in our research work 
and are therefore described together. As seen in figure 1, the shorter the 
push distance, the higher the production, until the blade becomes full and the 
operator dumps the load. This is referred to as the blade-full point. If the 
push distance is less than this, production will drop off because the blade is 
not full when the tractor dozer reaches the dump point. Consequently, the 
nearer the tractor dozer works to the blade-full point, the higher production 
rates will be. There are two techniques that an operator can employ to accom- 
plish this: 

1. Use angle blades that move material short distances laterally towards 
the outslope under continuous cutting and casting (blade-full) conditions. 

2. Use narrow deep blades that fill in short distances and carry large 
volumes. 



The first technique is extremely productive in normal 90- to 120-foot 
crest-to-crest spoil because the blade travels parallel to the spoil bank, 
moving the material laterally towards the outslope. The average push dis- 
tances are, therefore, approximately one-half the width of the blade. Also, 
the blade operates in a continuous cutting and casting action as it moves 
along the spoil bank, which means that it is always working at the blade-full 
(optimum) point. High production rates result from this as well as from the 
fact that the nonproductive backing and positioning time of the dozer is 
eliminated. 



The second technique is employed when push distances are short and the 

blade is not filled when the operator reaches the dump point; such is the case 

when the push distances are too great for angle dozing but short of the blade- 
full point. 

Both of these techniques were researched and evaluated through a joint 
program between the Pittsburg and Midway Coal Co. (P&M) and the U.S. Bureau of 
Mines (USBM) . The outcome of the 18-month research effort was a combination 
of highly productive specialized tools that can be used in combination with 
conventional tractor dozers and scrapers. The tools are shown in figures 5-8 
and include 

1. 48-foot angle blade. 

2. 24-foot U-blade. 

3. 13-foot narrow, deep U-blade. 

4. 24- foot grading bar. 

The 48-foot angle blade proved to be the workhorse of the team and is the 
result of many months of work designing and field-testing various types and 
sizes of blades. The angle blade is mounted on two 410-horsepower tractors in 
an offset configuration, but requires only one operator. The blade is fixed 
at a 45° angle. The angle blade usually begins its cycle at one end of the 
spoil bank, where the operator fills the blade and moves forward, casting the 
spoil material laterally to the outslope. This continuous cutting and casting 
motion continues the full length of the spoil bank at a speed of approximately 
1.5 miles per hour. At the opposite end of the bank, the operator turns the 
system around and begins cutting and casting material into the opposite valley. 
The process continues until adjacent spoil banks meet or the lateral reloca- 
tion distance from the centerline of the spoil bank exceeds approximately 
50 feet. 

The field evaluation of the 48-foot angle blade over a period of 520 oper- 
ating hours showed an average production rate of approximately 6,000 to 6,500 
BCY/hr. When used in conjunction with other specialized tools and conven- 
tional dozers as support, the system reduced overall work efforts and cost by 
approximately 50 percent. These reductions were achieved under very controlled 
field conditions, and it was estimated that the reduction would be 30 to 
40 percent under actual mining conditions. This fact was later proven to be 
the case and will be discussed shortly. 

The side-by-side offset configuration of the tractors was adopted from an 
existing system marketed by a major tractor dozer manufacturer which consists 
of two tractors side-by-side with a large single U-blade. The value of this 
system was recognized and adopted for the angle blade. In addition, a 24-foot 
U-blade was purchased for the two tractors, and the system was used as a sup- 
port tool in normal spoil and as the prime mover in box-cut spoil. The 
24-foot U-blade showed an approximate 25 percent increase in production and 
25 percent decrease in fuel consumption over two single tractor dozers working 
separately. In addition, there was an immediate reduction in cost for labor 
because the system, like the angle blade, requires only one operator. 




FIGURE 5. - Forty-eight-foot angle blade mounted on two side-by-side tractors in an 
offset configuration. 




FIGURE 6. - Twenty-four-foot U-blade mounted on two side-by-side tractors. 



10 




FIGURE 7. - Thirteen-foot narrow, deep U-blade. 




FIGURE 8. - Twenty-four-foot grading bar. 



11 



5,000 



O 4,000 

tr 

LlI 
Q_ 

CO 3,000 
Q 

< 

>- 

^ 2,000 

m 

O 

UJ 
CO 

o 
o 



1,000 — 



— 


V — Angle blade 




I 50 feet 

\ 1 


— 


\ 

\ r Narrow, deep 
\ reclamation 1 


J 
Dlade 


f 1 


Conventional U 
bul Idozer 

i i i 


1 1 



10 20 30 40 50 60 70 80 

HORIZONTAL RELOCATION 
DISTANCE, feet 

FIGURE 9. - Effective relocation ranges for specialized 

and conventional blades. 



us to the second technique by which an operator 
using a narrow, deep blade that fills in short d 



The value of conven- 
tional bulldozer techniques 
in land recontouring was not 
diminished in the success of 
the 48-foot angle blade and 
24-foot U-blade. The field 
evaluation showed that the 
angle blade could handle 60 
to 80 percent of material 
that had to be moved ; the 
remaining 20 to 40 percent 
had to be handled by conven- 
tional dozers. It was also 
observed that these conven- 
tional dozers required 40 or 
more feet to get a full 
blade. As it turns out, 
this is beyond the effective 
relocation distance of the 
48-foot angle blade as seen 
in figure 9. If conditions 
are adverse , such as in 
rocky material, the blade- 
full point for dozers could 
be as much as 70 feet, and 
yet the required push dis- 
tance may only be 50 feet. 
The consequence, of course, 
is that the operator will 
dump the load before the 
blade is full, which brings 

can increase production: 

istances . 



In an effort to study this technique a specialized 13-foot, narrow, deep 
U-blade was designed and tested under the P&M-USBM contract. A comparison of 
the blade's specifications with those of a conventional U-blade for a 
410-horsepower tractor is shown in table 3. 



Results of the field test of the deep U-blade show that it could fill in 
30 to 40 feet by sidecutting as seen in figure 9 and was very effective in 
combination with the angle blade in leveling and reshaping spoil banks. The 
blade design does not represent a major modification in blades; it is an 
improvement in a tool for a specific job. It is not too specialized to be 
used for other routine jobs in surface mining, such as long-distance pushes in 
land leveling, building dragline pads, or even building roads. 



12 



TABLE 3. - Dimensional comparison of conventional U-blade and narrow, 
deep U-blade for a 410-horsepower tractor 



Conventional 


Narrow, deep 


U-blade 


U-blade 


15.75 


13.0 


5.92 


5.75 


9,280 


8,950 


37 


40.5 


25 


30 


4.21 


3.0 


26.5 


23.0 


47.0 


54.0 


26.5 


23.0 



Blade length f t . . 

Blade height f t . . 

Weight (blade only) lb . . 

Width (front to back of 

side plate) in. . 

Wing angle deg . . 

Length of each wing f t. . 

Left wing pet of length. . 

Center section pet of length.. 

Right wing pet of length. . 



The grading bar, as seen in figure 8, was designed to smooth the rough- 
graded land in preparation for the farming phase of land reclamation. It 
represents another tool designed to perform a specific job at a cost savings 
to the mine operator. 

A number of drag systems, such as I-beams, pipes, and large-diameter wire 
rope, have been used. However, they all have several basic drawbacks: they 
will occasionally hang up on large rocks, they require a large turning radius, 
and they are difficult to operate in limited space areas such as a point of 
land extending into a water impoundment. 

The grading bar is based on the idea of pushing the finishing tool rather 
than dragging it. It is made from 24-foot channel iron, with side wings for 
carrying live soil, and is mounted under the heel plate of a conventional bull- 
dozer blade using two 2-inch pins. Mounting time is about 5 minutes. Under 
operating conditions, the blade support arms rest on top of the channel iron, 
and the cutting edge of the bulldozer's blade can penetrate the ground about 
1 inch. The operator has full control over lift and tilt of the grading bar, 
since it is attached to the blade. 

The grading bar was tested under the P&M-USBM contract and smoothed 
1,431 acres at rates between 2.5 and 7 acres per hour, depending on ground 
conditions. It was mounted on a 270-horsepower tractor dozer. 

The major conclusions drawn from field-testing all of the specialized 
tools under the P&M-USBM contract follow: 

1. The tools designed and tested to work in the short distance reloca- 
tion range performed satisfactorily and resulted in a 50-percent reduction in 
cost and tractor time per acre of mined land leveled and reshaped. Propor- 
tional savings in diesel fuel were also experienced. 

2. In leveling and shaping normal 90- to 120-foot crest-to-crest spoil 
banks, the 48-foot angle blade moved approximately 80 percent of the material 
while using only 60 percent of the total tractor time. 



13 



3. Conventional bulldozers are needed in the final stages of the land-shaping 
process. They will move an estimated 20 percent of the total material but will 
require approximately 40 percent of the total tractor time. 

4. The 24-foot U-blade showed a 25-percent increase in production over two 
separate tractor dozers of comparable horsepower. 

5. The deep U-blade demonstrated higher production rates than conventional 
U-blades in short-distance relocation range below the blade-full point; above this 
point, the deep U-blade was comparable to conventional blades. 

6. The grading bar demonstrated its efficiency in smoothing rough-graded land 
at rates between 2.5 and 7 acres per hour depending on ground conditions. 

7. No single tool was effective in all situations. It required the combina- 
tion of tools to effectively and efficiently level and shape the spoil banks. 

Based on the results of the P&M-USBM contract, a technology transfer project 
was funded to demonstrate the tools developed and to show that significant reduc- 
tions in cost and work efforts could be realized by employing the proper combination 
of specialized and conventional tools. The mine site was in Texas, and the con- 
tractor selected to contract the demonstration was Russell and Sons Construction Co. 

The team for the technology transfer demonstration was on location in mid- 
February 1979; field testing began around March 1 and continued until September. It 
included the same four specialized tools developed and/or tested under the P&M-USBM 
contract (figs. 5 through 8) along with conventional dozers. One exception was that 
a low-ground-pressure (LGP) tractor dozer was brought in as a support tool when the 
ground conditions were wet and flotation was a problem. The LGP had a ground bear- 
ing pressure of approximately 6.3 psx as compared to 13 to 15 psi for the other 
tools. It was used primarily in unstable soil conditions as well as in finish 
grading. 

The demonstration was conducted in five test areas located throughout the mine. 
The five areas, totaling 312 acres, included 120-foot crest-to-crest spoil areas and 
box-cut spoil. The field results are shown in table 4 and equate to a 32-percent 
decrease in cost and fuel for normal spoil and a 27-percent decrease in cost and 
fuel for box-cut spoil, compared with costs using conventional equipment. 

TABLE 4 . - Results of technology transfer demonstration in Texas 





Location and type of spoil 




Area 1 , 


Area 2 , 


Area 3 , 


Area 4, 


Area 5 , 


Total or 




box-cut and 


box-cut and 


box-cut and 


irregular 


irregular 


average 




irregular 


irregular 


irregular 








Approximate number 














of working days.. 


26 


26 


43 


34 


25 


154 


Acres reclaimed... 


38 


49 


83 


68 


74 


312 


Acres reclaimed 














per working day.. 


1.46 


1.88 


1.93 


2.00 


2.96 


2.03 


Total horsepower- 














hours per acre... 


6,904 


7,912 


9,049 


5,363 


4,717 


6,778 



As a result of the excellent performance of the specialized equipment, the man- 
ager of the mine adopted the equipment as his primary land-leveling and recontouring 
tools. 



14 



Operator Skills 

This is the fourth job condition mentioned earlier which the USBM is 
researching for possible reduction in mined-land recontouring costs and work 
effort. This also leads us to the following, second major topic of this paper, 
as discussed in the following section. 

BULLDOZER WORK RATE INDICATOR 

The work rate indicator is actually a draft power sensor system designed 
to help the bulldozer operator to maintain high production rates without first 
acquiring extensive operator skill . This system continuously measures both 
the push of the blade against the spoil and the true ground velocity of the 
bulldozer. It multiplies those quantities to determine the real work rate of 
the machine. The system consists of a velocity sensor, a blade load sensor, 
processing circuits, and a work rate indicator. 

The processing circuits include an analog multiplier which has an output 
signal representing the draft power (velocity X load = power) . The draft 
power, or pushing power, is a measurement of the work rate at that moment. 

The velocity sensor consists of an ultrasonic continuous wave transmitter 
and receiver operating at a fixed transmission frequency. This sensor is 
housed in a metal container located behind the operator's cab (fig. 10). 




FIGURE 10. • Velocity sensor mounted behind operator's cab. 



15 



The signal from the velocity sensor transmitter strikes the ground behind 
the bulldozer and is partially reflected back to the receiver. When the bull- 
dozer is moving forward, there is a reduction in the frequency at which the 
signal is received. 

The load sensor is a strain gage installed on the neck of one of the push- 
beam trunnion's balls (fig. 11). The neck is highly stressed when the resist- 
ance of the load is transmitted through the blade and the push-beams. 

An audible beeper was the indication preferred by the operators. The 
number of beeps per second increases as the work rate increases. Each beep is 
about 1/10 second long and consists of a tone burst of low sonic frequency, 
approximately 400 Hz. A blinking light display and meter are also available. 
These displays, the beeper, and the processing circuitry, are contained in a 
rugged metal box mounted in the cab area. 

As the bulldozer moves forward with the blade up and away from the ground, 
the work rate will be zero. Because the product of the velocity (say 1.5 mph) 
multipled by the zero load against the blade is zero, the beep rate produced 
is essentially zero. 

As the blade is lowered and digs into the ground, a load is put on the 
blade and beeping begins. As the blade pushes more material, the load 
increases and so does the beep rate until the maximum work rate is reached. 

Depending on the resistance of the material being moved, the horsepower 
available at the tracks, and the traction conditions, the bulldozer can reach 
the combination of velocity and blade load that produces the maximum work rate 
possible for those conditions. Once the beeping reaches the fastest rate 
attainable for those conditions, the operator attempts to maintain that rate. 
This is usually done by raising or lowering the blade. 



Electronic circuit box 



True ground 
speed sensor 




Draft force sensor 

FIGURE 11. - Location of draft force sensor and electronic circuit box. 



16 



For example, if the blade is allowed to penetrate too deeply and the load 
against it becomes too large, the bulldozer will lose speed, either because 
the tracks slip or because the engine slows down. As the bulldozer work rate 
decreases, the beep rate will decrease proportionally. The operator must par- 
tially raise the blade to again achieve an optimum combination of velocity and 
blade load. Moving into an area of reduced traction would normally cause a 
similar indication and a lower work rate due to slippage. The correction 
would be similar. 

On the other hand, if the beep rate dropped while the bulldozer velocity 
increased, this could indicate to the operator that the load against the blade 
had decreased. The work rate might increase if the blade were lowered. The 
system works regardless of the change in dozing conditions. 

The prototype system, which was developed by the Southwest Research 
Institute under a Bureau of Mines contract, was field-tested early in 1978 at 
a large lignite mine in Texas. 

Two 410-horsepower bulldozers were fitted with this system and used for 
leveling and recontouring spoil banks. A test area of 105 acres was divided 
into smaller areas to accommodate various tests. 

Several operators ran the bulldozers both with and without the use of the 
work rate indicator. Logs were kept showing machine time, identity of the 
operator, weather conditions, fuel consumption, and other pertinent data. 
Tests were run for approximately 3 months. 

The data showed that when the work rate indicator was used, the land was 
recontoured faster, providing a potential for reduced labor and capital costs. 
Furthermore, less fuel was used per acre. The volume of material moved per 
hour increased between 20 and 25 percent in the various test areas. 

Although the hourly rate at which the bulldozers consumed fuel increased, 
this effect was more than offset because fewer hours were required to level 
and recontour an area. The approximate results follow: fuel consumption per 
hour, up 7 percent; hours of bulldozing required per acre, down 25 percent; 
fuel consumption per acre, down 20 to 25 percent. 

The prototype design is being production-engineered as a rugged product, 
readily installed and used on existing reclamation bulldozers. A series of 
field tests of this improved system will be conducted on bulldozers of several 
different manufacturers and sizes. Results should be available in late 1980. 

BACKFILLING FINAL HIGHWALLS WITH DRAGLINES 

Public Law 95-87 mandates that all mined land be returned to approximately 
the original contour with all highwalls eliminated. The regulations actually 
specify that the backfilled slopes covering the highwall cannot exceed the 
approximate premining slopes. 



17 



The major problem confronting the mine operator in complying with the 
regulations is moving large volumes of material over long distances under con- 
ditions that will vary depending on the original ground contour (flat, rolling, 
etc.)> overburden thickness, and the orientation of the coal seam(s) (flat or 
dipping) . 

At present, the industry is relying primarily on tractor dozers, drag- 
lines, scrapers, and trucks to move the required material; this is logical 
since such equipment is usually available at the mine site or at least the 
operator is familiar with it. 

A number of studies have been, and are continuing to be, conducted by the 
mining industry and the Government on various methods for eliminating high- 
walls. Most of the methods include the utilization of the above-mentioned 
equipment with varying modification as to size, deployment, combinations, etc. 
This section of this paper will address an evaluation of several types and 
combinations of equipment for backfilling highwalls in modified area mining. 

The mine site selected for the evaluation is in eastern Ohio and involves 
three different pit configurations: 

1. Pit A, which was excavated by a medium-size shovel (less than 60 yd ) . 
See figure 12. 

2. Pit B, which was excavated by a small dragline (less than 40 yd ) . 
See figure 13. 

3. Pit C, which was excavated by a large dragline (greater than 100 yd ) . 
See figure 14. 

Three basic approaches were selected for backfilling the highwalls in 
each of the three pits. The three approaches include 

1. Conventional tractor dozers. 

4 

2. Conventional dragline working on the spoil side of the pit. 

3. Conventional dragline working on the highwall side of the pit. 
The specific equipment for each approach for pits A and B included 

1. Conventional tractor dozers — 410-horsepower units. 

2. Conventional dragline — 11-cubic-yard diesel with 170-foot operating 
radius. 410-horsepower tractor dozers were used for support work as required. 

3. Conventional dragline — same as above except had a 20-cubic-yard 
crescent-shaped bucket and 600 feet of hoist and drag rope. 410-horsepower 
tractor dozers were also used for support work. 



18 




FIGURE 12. - Typical cross section of pit A. 




FIGURE 13. - Typical cross section of pit B. 



y rvininol gro» n _j. 




FIGURE 14. - Typical cross section of pit C. 



For pit C, the specific equipment included 

1. Conventional tractor dozers — 410-horsepower units. 

2. Conventional dragline — 35-cubic-yard electric dragline with 201-foot 
operating radius. 410-horsepower tractor dozers were used for support work. 

3. Conventional dragline — same as above except had a 60-cubic-yard 
crescent-shaped bucket and 800 feet of hoist and drag rope. 410-horsepower 
tractor dozers were used for support work. 

The procedure for moving the spoil in each of the three approaches was 
the same for all pits. In the first approach, the tractor dozers moved the 



19 



material from the spoil side to the pit in a series of cuts in three primary 
lifts. The first lifts involved pushing approximately 25 percent of the 
required spoil material down a slope of 9.6 percent (5.5°) at a rehandle of 
25 percent. The second lift involved pushing approximately 50 percent of the 
material over a zero percent slope (±2.0 pet) at a rehandle of 40 percent. 
The third lift involved pushing the remaining 25 percent up a slope of approxi- 
mately 17.6 percent (10°) at a rehandle of 25 percent. There was sufficient 
material in the spoil banks to backfill the highwall and attain the final 
slopes, as seen in figures 12-14; consequently, material from other locations, 
such as the box-cut spoil, was not required. 

In the second approach, the dragline is placed on a bench prepared by a 
dozer on the spoil side of the pit as seen in figure 15. The dragline was 
positioned to obtain the maximum dumping range. The dozers assisted the drag- 
line by pushing spoil to the loading zone if some spoil material could not be 
reached. The tractor dozers also did the final grading in the pit spoil area 
and filled in any areas that the dragline could not reach. 

In the third approach, the dragline was placed on top of the highwall 
(fig. 16) and equipped with additional hoist and drag rope along with a 




nrnvofmuJIU" ' Ui 



FIGURE 15. - Dragline backfilling from spoil side of pit. 




s s s 

FIGURE 16. - Dragline backfilling from highwall side of pit. 



20 



crescent-shaped bucket for dragging the material into the pit similar to a 
tower excavator. A 300-horsepower track- type pipelayer was used for the tail- 
block assembly. The dragline-tower system was able to reach all required spoil 
material. The final leveling and grading work was done with 410-horsepower 
tractor dozers. 



Specifics about each pit follow. 

Pit A 

Because the pit (fig. 12) contained several inside and outside curves, 
its length of 2,636 feet was divided into six sections; each was evaluated 
separately and the results were compiled for each of the three combinations of 
equipment. The average highwall height was approximately 88 feet, and the 
average pit width was 70 feet. Each linear foot of highwall required an aver- 
age of 273 BCY of spoil to backfill to the top. For this study it was assumed 
that no blasting would occur to facilitate backfilling. The average spoil 
relocation distance from the centroid of the cut area (required spoil) to the 
centroid of the fill area was 203 feet. Results of the analysis are shown in 
table 5. 

TABLE 5 . - Summary of results for pits A, B, and C 





Conventional 


Dragline 


Dragline 


Pit and primary 


dozers 


on si 


)oil 


on highwall 


recontouring equipment 


Cost/ft 


Change, 


Cost/ft 


Change , 


Cost/ft 


Change , 




highwall 


pet 


highwall 


pet 


highwall 


pet 


Pit A: Small dragline 














with conventional 11-yd 














bucket and 20-yd 3 cres- 














cent bucket; conventional 
















$144 





$108 


-25 


$100 


-31 


Pit B: Small dragline 














with conventional 11-yd 3 














bucket and 20-yd 3 cres- 














cent bucket; conventional 
















144 





-120 


-17 


104 


-28 


Pit C: Dragline with 




conventional 35-yd 3 














bucket and 60-yd 3 cres- 














cent bucket; conventional 
















299 





151 


-49 


108 


-64 



NOTE. — Change percent is the difference from operation with conventional dozers , 

Pit B 



Figure 13 shows a typical cross section of pit B. Like pit A, this pit 
was divided into sections which were evaluated separately and the results com- 
pleted. The average highwall height is approximately 84 feet, the average pit 
width is approximately 90 feet, and the pit length is approximately 7 ,690 feet. 



21 



Each linear foot of highwall averaged approximately 264 BCY of spoil to back- 
fill to the top. As in pit A, it was assumed no blasting of the highwall 
would take place. The average spoil relocation distance was 236 feet. Results 
are shown in table 5. 

Pit C 

Figure 14 shows a typical cross section of pit C. In comparison to pits 
A and B, this pit necessitated a major deviation in some equipment because of 
its size and required spoil material for backfilling of the highwall; however, 
deployment of equipment and movement of material was essentially the same. 
The average overall highwall height is approximately 138 feet; the average pit 
width is approximately 140 feet with an average bench width of approximately 
30 feet. The pit length is approximately 800 feet. Each linear foot of high- 
wall required approximately 352 cubic yards of spoil material to backfill to 
the top of the bench. As in pits A and B, it was assumed no blasting of the 
highwall would take place. The average spoil relocation distance was 292 feet. 
Results are shown in table 5. 

Summary 

It is apparent, from at least this study, that the potential exists for 
gaining some significant cost savings in backfilling highwalls by using drag- 
lines either sidecasting or dragging material from atop the highwall. The 
next step is to conduct a comparative field evaluation study of the three sys- 
tems at an active mine site. This should provide reliable data for mine oper- 
ators to assess their backfilling requirements in modified area mining 
employing these combinations. 

CONCLUSION 

The primary approach Bureau research has taken to date in its efforts to 
reduce costs for recontouring mined land is to develop relatively inexpensive 
attachments for existing machines that will convert them to high-volume, low- 
cost tools. Emphasis is on the development of specialized tools to assist the 
operator until such time as (1) the industry develops systems that do not pile 
the spoil, or (2) enough surface coal mines increase production and their 
mined acreage to warrant using large expensive land-leveling equipment solely 
for recontouring mined land. 

BIBLIOGRAPHY 

1. Caterpillar Performance Handbook. Caterpillar Tractor Co., Peoria, 111., 

9th ed., October 1978, pp. 4-17 through 4-26. 

2. Goris, J. M. , and H. S. Benson. Maximizing Dozer Work Rate With Draft 

Power Sensing Systems. Pres. at Earthmoving Industry Conference, 
Peoria, 111., Apr. 23-25, 1979, SAE Paper 790510, 11 pp. 

3. Howland, J. W. Application of High Volume Earthmoving Methods to the 

Reclamation of Area Mined Spoil Banks. Final Report to U.S. Bureau of 
Mines, Contract No. HO252012, February 1978. 



22 



DESIGN CONSIDERATIONS OF TERRACE-PIT MINING 

by 
Gregory G. Miller 1 



INTRODUCTION 

A dragline is the least expensive method to strip overburden where simple 
digging and casting are used. However, deep overburden, dipping seams, faulted 
seams, multiple seams, thin interburden, and toxic materials make dragline min- 
ing procedures very complex, and in any of these situations it is questionable 
whether dragline stripping is the best mining method. Other mining equipment 
such as shovels, bucket wheel excavators, scrapers, and backhoes may be better. 
Such equipment is best used where benches or terraces must be constructed to 
reach a deep coal seam. Figure 1 shows a typical shovel-truck equipment 
system terrace-pit-mining a single coal seam. Here four terraces are used to 
mine the overburden and one terrace to dig the coal. The benches are level 
and trucks haul the spoil around the pit to be back-dumped. In this way, the 
pit is continuously backfilled and reclaimed as the mine progresses. 

RECTANGULAR PROPERTY SHAPE 

If the terrain is flat and the coal seam has practically no dip, a long 
and narrow, rectangular property can be mined in two panels with one turn- 
around. The turnaround allows a better face length and places the second 
panel's final void close to the first panel's box-cut stockpile. The final 
void can then be completely backfilled with the box-cut material. In a 
rectangular mine, the faces should be advanced in parallel. If the mine needs 
to produce 20 million tons of coal per year for 40 years, a 15-square-mile 
property is needed with a 50-foot coal thickness. If the property is two 
sections wide and eight long, the above two-panel technique can be used. But 
if it is four sections square, four panels may be necessary to keep an optimal 
face length and still place the final void near the original box-cut stockpile. 

CIRCULAR PROPERTY SHAPE 

In the Western United States, it is rare that mine property be other than 
rectangular. However, surface terrain and the coal itself may make the actual 
mine property shape circular. Here the optimum pit shape may be circular and 
instead of advancing the faces in parallel, the faces are rotated around the 
center of the circle, with the face length equal to its radius. Sectorial 
panels are used again, depending on how the terrain rises and falls, and 
concentric panels may also be used and advanced to or retreated from the 
center. 



Mechanical engineer, Spokane Research Center, Bureau of Mines, Spokane, Wash. 




FIGURE 1. - Single-seam shovel-truck terrace-pit system. 



DIRECTION OF ADVANCE 



If the coal seam is lying horizontally or dips slightly (up to 3°), 
advance can be essentially in any direction as long as the terrain is flat. 
This condition is preferred in terrace-pit mining because coal production will 
remain uniform. However, geotechnical factors, ground water, or location of 
toxic zones in the overburden may dictate the direction of advance. In the 
case of slightly dipping seams such as those found in the Powder River Basin, 
if the coal does not cropout within the mine property boundary, an area should 
be chosen with the least amount of box-cut spoil to initiate mining. In cases 
of rising terrain and horizontal coal seams, it is usually preferred to 
advance perpendicular to the rising terrain if stability of the material 
permits, because of the reduced strip ratio in the first panel. If the mine 
property is rectangular but the seam dips about 3°, it is generally recommended 
that the mine advance along the strike. However, the mine can also proceed 
along the dip. The decision partly depends on how the property lies to the 
dip, and if it is long and narrow or nearly square. However, economics play 
a major role in deciding whether to advance downdip or along the strike. For 



24 



< 

or 



Q_ 

Q_ 




20 
MINE LIFE, years 

KEY 

Mining along strike with two panels and open slot 
Mining along dip with four panels and open slot 
Mining with no slot left open 



a mine situation where the 
length of the mine property 
occurs along the strike, 
advancing the first panel 
along the strike is very 
economic for the first half 
of the mine life because of 
its low stripping ratio. 
However , there is a great 
danger that the coal will 
not be mined on the second 
panel because of its higher 
stripping ratio. Figure 2 
shows the relation between 
the stripping ratio and a 
mine life of 40 years. Dur- 
ing the first 20 years the 
first panel's stripping 
ratio average remains uni- 
form; then as the mine turns 
to mine the second panel, 
the stripping ratio jumps up 
dramatically to a level to 
be maintained for the last 
20 years. If a slot is not 
left between the two panels, 
a portion of the first panel 
must be rehandled in mining 
the second panel. This 
raises the second panel's 
average stripping ratio. 



FIGURE 2. - Change inthe stripping ratio overthe life of a 
rectangular mine property with a dipping coal 
seam subcropping along its long side. 

If this same property is 
mined along the dip, four panels will be necessary. Figure 2 shows how the 
stripping ratio will fluctuate over the life of the mine. At a 40-year site, 
the first panel will proceed downdip, the second panel updip, the third downdip, 
and the fourth updip. If slots are not left between adjacent panels, the 
average stripping ratio will be the same as for the first panel. If slots are 
left, the last three panels will have a reduced stripping ratio. When mining 
downdip, problems result because there is less room to spoil the overburden 
into the previous cut. When retreating updip, the trucks may encounter haulage 
problems, but the waste is more stable, the ground water is drained from coal 
and overburden, and there is more space available for spoil. 



Generally, a terrace mine can operate on a 3° to 9° dip either along the 
strike or along the dip. However, when the coal dips more than 9°, the pit 
floor becomes too steep for truck haulage. Terrace-pit mining can still pro- 
ceed by two methods. One method is to mine neither along the strike nor along 
the dip, but at an angle to them. This tends to reduce the dip to a somewhat 
smaller angle. In the other method, the terraces are kept horizontal, and the 
coal is mined selectively with hydraulic shovels as the coal crops out in the 
bench. 



25 



NUMBER OF SEAMS 

The efficiency of coal mining depends on the thickness of the overburden, 
interburden, and coal seams. Thick coal seams and thin waste are preferred in 
all mining situations because of the low stripping ratio. However, multiple 
thin seams may be economic to mine even down to several hundred feet if the 
cumulative strip ratio is low and the mine is properly designed. 

GROUND WATER 

A small flow of ground water from interrupted aquifers can be allowed to 
drain into sumps cut into the pit floor and into the benches. The water can 
then be pumped out for uses such as dust control. If an aquifer of significant 
size will be interrupted, the mine must be properly designed to handle problems 
associated with wet overburden. Although this is not particularly a problem 
in the Powder River Basin or the Four Corners region, the Texas lignite region 
has areas of high flow rates and in some cases artesian pressures. Because 
artesian pressure in the underburden can cause floor heave and flood the pit, 
pumping wells should be placed in and around the pit to lower the water level. 

GEOTECHNICAL DATA 

Considerable premine research should be conducted to supply to the mine- 
design engineers critical geotechnical data on the properties of the site. 
This data will be used to determine the excavation equipment necessary and the 
layout of the mine that will prevent slope stability problems. Several oper- 
ators have had to redesign their mines at a considerable financial loss 
because the excavator was unable to dig the overburden. There are cases where 
the excavator became spoilbound because the swell factor was not properly 
determined and cases where the stability of the waste and overburden was not 
considered important, resulting in slope failures. 

TERRACE HEIGHTS 

Terrace heights will vary in a multiple-seam mine because the interburden, 
overburden, and coal seam thicknesses change. The slope of the land or the 
pitch of the coal seam causes the terrace height to change as the mine pro- 
gresses. Significant changes will require the addition or deletion of terraces 
and their side-pit haulroads. Generally, the height should be designed to be 
as near optimal for the loading equipment as possible. 

TERRACE WIDTH 

Any unnecessary bench width will increase haulage distance and costs. 
Therefore, all terraces, including the exposed coal seam, should be kept to a 
minimum width. The benches should be around 100 to 150 feet wide to permit 
equipment passing and turnaround, and to minimize congestion in the loading 
area. Generally, their width and haulroad width should be at least three times 
the maximum vehicle width, thereby enabling two haulage vehicles to pass 
maintenance equipment without interrupting production. However, the produc- 
tion rate or the excavator size may also be the determining factor of the 
final bench width. 



26 



SPECIAL TERRACES 

The geological and physical characteristics of the various overburden 
strata encountered may require different equipment combinations or separate 
terraces. For example, unconsolidated overburden and easily fragmented rock, 
like certain shales, may be most economically excavated by scrapers, while 
other material, like sandstone, might be best excavated by a shovel-truck team. 
In addition, if a toxic layer of overburden exists in sufficient quantity, a 
special terrace should be included in order that the material can be exca- 
vated and deposited in the most beneficial location. 

SPOIL TERRACES 

Spoil terraces should be kept on the same level as the excavation terrace 
so that negative grades will not be encountered. If special toxic material 
terraces are used in excavation, a counterpart spoil terrace will be needed. 
This may be at a different level than its excavation terrace, thereby encoun- 
tering adverse grades and reduced production. This toxic spoil terrace should 
be located at a level in the spoil profile to sufficiently isolate the mate- 
rial from contact with the environment. 

FACE LENGTH 

Determining the optimum face length is difficult because it depends on 
many variables. It is usually done in the detailed planning stage of an 
actual mine. Often property boundaries do not allow the use of the optimum 
face length, so a compromise is necessary. A whole number of panels must be 
planned to fit into the property, and an even number of panels is preferred 
because it positions the final voids near the original box-cut stockpile. In 
a case of an irregular property boundary that intersects the faces, a variable 
face length could be used to uncover all the coal. However, once mining is 
initiated, a significant deviation from the planned face length could require 
an extensive redesign of the mine. 

Long face lengths are not desirable because of the numerous excavators 
required. In addition, Federal and State regulations may prohibit long faces 
because they represent an extensive source of interruption of the environment. 
The rate of face advance also may be less than backfilling requirements call 
for. However, a large production rate from a single pit may dictate the use 
of a long face. In such cases, coal and overburden haulage through the middle 
of the pit may be desirable. On the other hand, a short face would dictate a 
series of narrow panels. This is not desirable because the length of coal 
haulage roads would be continually fluctuating. Short faces require wide 
benches and a longer pit to maintain production levels. 

METHODS OF TURNING 

When a panel has advanced to the end of the property, the mine must 
execute a 180° turn into the next panel. This can be done three ways. First, 
the turn can be performed with two 90° turns. In this method, the technique 
of advancing the faces in parallel is maintained. When the mine has advanced 



27 



to the end of the panel, the shovels are turned 90° and begin excavating the 
next panel. This short turning panel is advanced to the full width of the new 
panel while backfilling the void in the first panel; then the excavators are 
turned 90° again and begin retreating that panel, normally to its full length. 
Second, a 180° turn can be executed by rotating the pit around a point common 
to both panels with the radius of the swing equal to the face length. This 
method is similar to that used in mining properties that are nearly circular. 
Sectorial panels are used, and some corner coal may be lost. Third, another 
turn may be performed if new equipment will be purchased at the end of 20 
years. Here a box-cut can be developed in the next panel before the first 
panel is complete. When the first panel finishes, it can backfill its void 
with the second panel's box-cut material. These three turning methods are 
quite complicated to execute and will require constant pit monitoring. 

SPOIL SLOTS 

When two or more panels are required for the mine property, it is bene- 
ficial not to backfill a wedge-shaped portion of the pit immediately adjacent 
to the next panel. This creates an open area, called a slot. By not back- 
filling this slotted area, rehandling of the previous panel's spoil to expose 
all coal is not required upon turning and retreating along the next panel. 
Generally, there will be spoil room available for constructing slots every 
panel. This results in each panel's waste being shifted over the width of the 
slot when backfilling takes place. The creation of a slot in the first panel 
may require overdeepening of its backfill area or stockpiling to dispose of 
the excess material caused by leaving the slot open. Savings in rehandling 
in subsequent panels should offset these costs. Two-panel property requires 
one slot whereas four-panel property requires three slots. 

In two-panel property with a 40-year life, portions of the slot could 
be open up to 40 years. Certain regulatory permits may be required for slots 
because of this long-term exposure. Slope reduction and revegetation of the 
slot highwalls may be necessary, or slots may be banned in favor of complete 
backfilling to the original contour. 

COAL HAULAGE 

The coal haulage road can be through the middle of the pit or along the 
edge of the pit where the panels meet. The overburden and coal haulage costs 
will dictate its location. For a shovel-truck terrace-pit mine, if the face 
is shorter than 4,700 feet, a side panel coal haulroad is preferred because 
this layout allows higher average truck speeds and lower costs per ton-mile. 
In this situation the slot between panels can be used for coal haulage, or the 
coal can be taken directly in-pit to the surface and hauled to the tipple. If 
the slot is used, it can also become the coal haulroad in the next retreating 
panel. 

When the face length for a shovel-truck mine exceeds 4,700 feet, it is 
preferable to have the coal haulroad through the middle of the pit because 
overburden and coal haulage distance become excessive. A coal haulroad slot 
can be left in the middle of the panel, but the use of two slots, the slot 
between adjacent panels and a coal haulage slot, may not be feasible. 



28 




FIGURE 3. - Multiseam scraper terrace-pit system. 

Figure 3 shows coal being hauled directly to the surface. Generally coal 
haulage through the side slot is preferred, because coal can be hauled up a 
shallow incline to the surface, rather than up steep in-pit haulroads. The 
spoil slot or wedge should be wide enough to permit two coal haulage trucks 
and a road grader to pass simultaneously. Because of this required road 
width, the advantages of reduced rehandle and the low grade of the haulroad 
may not be fully realized, because the slot must be either partially backfilled 
or increased in overall size to obtain a wide haulroad. This increases spoil 
rehandling. In addition, the slot slope angles may need to be reduced for 
long-term stability. 

OVERBURDEN HAULAGE 



Overburden is hauled to one side of the pit only to avoid interference 
with the coal haulroad; for example, when a side-pit coal haulage slot is 
used. Overburden haulage on the same side as coal haulage would require steep 
ramps down into the pit and back up to the spoil terraces. These roads are 
hard to maintain, lower production because of adverse grades, and are had on 
equipment. Overburden haulage from one side of the pit, opposite coal haulage, 



29 



is preferred because level roads can be maintained. If midpanel coal haulage 
is used and no slot is left, coal haulage can be along both pit sides and 
through the middle. Terrace-pit mining requires constant overburden haulroad 
construction and backfilling as the mine progresses. 

EXCAVATING EQUIPMENT 

Bucket-wheel excavators (BWE's) appear to have potential in the Texas 
lignite region and possibly in North Dakota where the overburden is uncon- 
solidated. They cannot be used effectively to dig material that needs to be 
blasted. They can follow the lignite on dips up to 3°, but for steeper dips, 
horizontal benches should be maintained. In this latter case, the lignite is 
selectively mined where the dipping coal crosses the highwall. In fact,\ a BWE 
can be quite effective where selective mining is necessary. A BWE can be very 
efficient in rebuilding the original stratigraphic sequence of the overburden. 
Generally, however, BWE's are relatively inflexible. They are designed for 
specific uses, and no significant deviation from planned mining techniques is 
possible. Therefore, if a BWE is to be used where flexibility may be required, 
the machine must be specially designed and set up. 

Competent overburden should be mined with shovels. Truck haulage can 
permit very selective rebuilding of the spoil and produce high spoil compac- 
tion. Trucks can operate economically in a one-way-haul distance of several 
miles within the range needed in terrace-pit mining. 

Scrapers can be used to terrace-mine unconsolidated overburden. 



30 



TOPSOIL ROCK REMOVAL 

by 
T. M. Brady, 1 W. W. Kaufman, 2 and D. N. Reynolds 3 



INTRODUCTION 

An important element of surface mining reclamation is topsoil since its 
quality is critical for obtaining successful revegetation of reclaimed land. 

In most surface mines, scrapers are used for topsoil removal, stockpiling, 
and redistribution. After topsoil redistribution, the soil must be prepared 
for revegetation or use as farmland. If the disturbed soil contains too many 
large rocks, farmland will not be as productive as originally. Farming in 
areas where no care has been taken to remove large rocks may result in damaged 
farm equipment and less water permeability, and in smaller, less desirable 
harvests. 

To ensure that the soil maintains its productivity and permeability, many 
States have enacted laws and policies to control the size and quantity of rock 
in the topsoil. On the Federal level, the Office of Surface Mining (OSM) has 
established strict regulations governing revegetation of the reclaimed areas. 
Removing rocks from the topsoil is a fairly easy task; however, maintaining 
productivity levels is much more complex, requiring years of monitoring. 

After topsoil redistribution, the soil must be prepared for revegetation. 
If there are too many large rocks in the topsoil, graders may be used to 
eliminate them prior to revegetation. Since this method does not penetrate 
the soil, it is often inadequate and does not comply with many regulations. 
When deeper penetration is desired, rock rakes attached to dozers are employed. 
Rakes can eliminate large rocks to depths of 18 inches and deeper, but do not 
remove the smaller rocks less than 6 inches in size. While the spacing of 
tines on rock rakes is easily adjustable, if the tines are spaced too close, 
the soil will be pushed in front of the dozer and rocks will not be eliminated. 

Since graders and rock rakes are not totally effective for rock removal, 
some mining companies have elected to use rock pickers. These pickers, which 
are not classified as mining equipment, are generally sold as farming equip- 
ment, and to date their use by the mining industry has been limited. 

Why aren't rock pickers popular within the mining industry? Often the 
topsoil is so plentiful and free of large rocks that there is simply no need 
for them. Also, since rock pickers are generally associated with the farming 
industry, mining companies simply may not have explored their potential for 
rock removal. 

iGeneral engineer, Spokane Research Center, Bureau of Mines, Spokane, Wash. 
2 Mining engineer, Energy Division, Skelly & Loy, Harrisburg, Pa. 
3 Geologist, Energy Division, Skelly & Loy, Harrisburg, Pa. 



31 



The following discussion outlines the extent of the rock problem through- 
out the United States, discusses in detail the legal requirements that affect 
the reclamation process, analyzes the state of the art of current rock pickers 
including their physical limitations, presents an analysis of rock pickers 
applied to mine reclamation, surveys environmental effects that may take 
place, and details the benefits that can result from introducing rock pickers 
into the mining industry. 

REGULATORY ROCK REMOVAL REQUIREMENTS 

For years surface mining was conducted without concern for future land 
uses. Consequently, the overburden strata were overturned, burying the origi- 
nal topsoil, and abundant rock fragments were introduced into the soils. The 
resultant deterioration of land utility has prompted the promulgation of regu- 
lations to insure every effort is made to restore mined areas to their original 
conditions. 

State Requirements 

As States became increasingly concerned with the adverse effects of sur- 
face mining, they began enacting and enforcing more stringent regulations 
governing mine operations. Among the adverse effects of surface mining that 
were identified was "rock pollution. " The contamination of the soils with an 
unnaturally high percentage of rocks and the prevalence of large rocks, at or 
near the surface, hindered revegetation efforts, especially where farming was 
attempted as a postmining land use. The current tendency of regulatory legis- 
lation is to aim toward requiring mine operators to return affected land to 
its original condition. Thus, the States having the most rock-free soil 
would need the most specific regulations on rock content limitations for the 
topsoil layer. However, with proper handling these regulations should not 
impose a hardship on the reclamation efforts. 

Table 1 provides a comparison of existing specific restrictions, implied 
regulations, and pending surface mine amendments. The States that are 
shown as having specified regulations are those defining limitations of rock 
size and/or percent in the topsoil layers of surface coal mine reclamation. 
Implied regulations are indefinite limitations pertaining to rock content in 
the topsoil layer. Such limitations are worded to the effect that "large 
rocks" will not hinder postmining land uses. The strictness of pending legis- 
lation was not discernible; however, almost all pending legislation was 
expected to reflect the intent of the new regulations promulgated by OSM. 

Among the States that are monitoring topsoil rock content, the most strict 
regulations are found in Illinois, Indiana, Kansas, Oklahoma, and Virginia. 



32 



TABLE 1 
STATE REGULATIONS ON TOPSOIL ROCK CONTENT 



STATE 


SPECIFIED 

STATE 

REGULATIONS 


IMPLIED 

STATE 

REGULATIONS 


z 
o o 

z K 

111 — 

a U 

111 

_l 


CURRENT POLICY 


Alabama 


O 


• 


o 


Replace as was 


Alaska 


O 


O 


o 


None 


Arizona 


O 


o 


•* 


None 


Arkansas 


O 


o 


• * 


None 


California 


O 


o 


•* 


None 


Colorado 


O 


o 


• * 


None 


Connecticut 


O 


o 


o 


None 


Delaware 


O 


o 


o 


None 


Florida 


O 


o 


o 


None 


Georgia 


o 


o 


o 


None 


Hawaii 


o 


o 


o 


None 


Idaho 


o 


• 


o 


Replace as was 


Illinois 


• 


o 


•* 


No 1 0" rocks in top 4 feet 


Indiana 


• 


o 


o 


Bury 6" rock at least 6" deep 


Iowa 


• 


• 


o 


Implemented interim OSM regulations 8/78 


Kansas 


• 


o 


• 


Bury 6" rocks at least 6" deep 


Kentucky 


o 


o 


• * 


Replace as was 


Louisiana 


o 


o 


•* 


Replace as was 


Maine 


o 


o 


o 


None 


Maryland 


o 


• 


•* 


Replace as was 


Massachusetts 


o 


o 


o 


None 


Michigan 


o 


o 


•* 


Replace as was 


Minnesota 


o 


o 


• 


Requires removal of 6" rocks from surface 


Mississippi 


o 


o 


•* 


None 


Missouri 


o 


o 


•* 


Requires removal of excess rock 



LEGEND: 



• Yes 



O No 



Will Conform to Office of Surface Mining 
(OSM) Regulations. 



33 



TABLE 1 (Cont'd.) 
STATE REGULATIONS ON TOPSOIL ROCK CONTENT 



STATE 


SPECIFIED 

STATE 

REGULATIONS 


IMPLIED 

STATE 

REGULATIONS 


z 
e> o 
z f= 

z <o 

UJ — 

a o 

UJ 


CURRENT POLICY 


Montana 


O 


O 


• * 


Replace as was 


Nebraska 


O 


o 


O 


None 


Nevada 


o 


o 


O 


None 


New Hampshire 


o 


o 


o 


None 


New Jersey 


o 


o 


o 


None 


New Mexico 


o 


o 


•* 


None 


New York 


o 


o 


o 


None 


North Carolina 


o 


o 


o 


Requires removal from tillable lands 


North Dakota 


o 


• 


• 


Requires removal from tillable lands 


Ohio 


o 


• 


o 


Requires removal from tillable lands 


Oklahoma 


• 


o 


• 


Adopted interim OSM regulations 


Oregon 


o 


o 


• 


None 


Pennsylvania 


o 


o 


•* 


Replace as was 


Rhode Island 


o 


o 


o 


None 


South Carolina 


o 


o 


o 


None 


South Dakota 


o 


o 


o 


Replace as was 


Tennessee 


o 


• 


•* 


Requires removal of 6" rocks from surface 


Texas 


o 


o 


•* 


Replace as was 


Utah 


o 


o 


•* 


None 


Vermont 


o 


o 


o 


None 


Virginia 


• 


o 


o 


Replace as was 


Washington 


o 


o 


o 


Replace as was 


West Virginia 


o 


• 


•* 


Must remove exposed boulders from surface 


Wisconsin 


o 


o 


o 


None 


Wyoming 


o 


• 


•* 


Replace as was 



LEGEND: • Yes 



O No 



* Will Conform to Office of Surface Mining 
(OSM) Regulations. 



34 



Federal Requirements 

OSM's permanent regulatory program does not have any regulations pertain- 
ing to the size or percent by volume of rocks in a reclaimed area. However, 
OSM does indirectly prevent an increase in rock content by requiring that each 
soil horizon (distinct soil layer) be removed separately, stored separately, 
and replaced as it was originally. This is aimed at eliminating the possibil- 
ities of mixing sublayer rock fragments into the upper soils and of overturning 
the strata. When the present study was funded, the interim regulations of OSM 
required less than 10 percent rock coarser than 3 inches, and permeability 
could not be less than 0.06 inch per hour in the top 20 inches. 

STATE OF THE ART OF ROCK PICKERS 

Characteristic Forms of Rock Pickers 

Many of today's rock removal devices have evolved from the potato farming 
business. As a result, most of the rock pickers are designed to pick rocks 
above 2 inches in minimum diameter. These rocks are removed prior to potato 
planting in order to reduce the number of stones harvested along with potatoes. 
Table 2 lists the general specifications of currently available rock pickers. 
In instances where companies manufacture more than one size of rock picker, 
only the largest models have been included in the table. 

The mechanisms used in rock pickers to separate the soil and the rock can 
be classified into four categories: potato chain, rotating rake, rotating 
cage, and passive rake. 




FIGURE 1. - Potato chain separation mode. (Adapted 
from Rockland Product literature.) 



Potato-Chain Rock Picker 

The potato chain 
(fig 1.) is the most common 
separation mechanism used 
to separate rocks from soils. 
These rock pickers are towed 
behind a tractor mounted on 
the draft arms of a three- 
point hitch. Power is 
obtained from the tractor's 
power takeoff (PTO) shaft. 
The rock picker consists 
of three basic components: 
the digging head, the 
conveying potato chain, and 
a storage hopper. 



35 



TABLE 2 
ROCK PICKER 



COMPANY 


MODEL 


HITCH 
TYPE 


RAKE 
BAR 


PENETRATION 


MAXIMUM 
ROCK SIZE 


MINIMUM 
ROCK SIZE 


HOPPER 

CAPACITY 

Cu. Yd. 


©Armor Metal 
Products 


Series E 


Standard 
P.T.O. 


Rotat- 
ing 


2 to 4" 


200 lbs. 


1 1/2" 


1.2 


©Bestland 


876 


Hydraulic 


Fixed 


2 to 3" 


1000 lbs 


1 3/4" 


1.2 


© Degelman 

Industries, Ltd. 


R-570-S 


P.T.O.- 
Pull 


Rotat- 
ing 


2 to 3" 


Not Available 


4" 


1.0 


©Harley Rock 
Picker Co. 


A-High 
Lift 


P.T.O. 


Rotat- 
ing 


2 to 3" 


20" 


2" 


1.1 


©Imperial Welding 
& Machine, Ltd. 


Mel Cam 

510 


Hydraulic 


Fixed 





44" 


3" 


0. 9 


©Leon's Manufac- 
turing Co. , Ltd. 


A-7500 


Hydraulic 


Rotat- 
ing 


2" 


20" 


2" 


2.3 


©Lockwood Corp. 


Hydra-lift 
L06630-00207 


P.T.O. 

540 


Vibrat- 
ing 


8" 


200 lbs. 


3/4" if 


1.25 


©McConnell Manu- 
facturing Co. Inc. 


Bin Type 


P.T.O. 
Standard 


Fixed 


6" 


10" 


2" 


1.5 


©Melroe Division 


8-D HiBoy 


Hydraulic 


Fixed 


4" 


200 lbs. 


2" 


0.9 


©N. P. Nelson 


to 


P.T.O. 
Standard 


Rotat- 
ing 


2 to 5" 


9" 


1 1/2" 


.75 


©Pratt Farms 


Model B 


P.T.O. 
Standard 


Fixed 


to 8" 


24" 


2" 


5.0 


© Rockland 

Manufacturing 


Rotoveyer 


3 Point 
Hitch 


Rotary 


12" 


10" 


2" 


8.0 


© Rock-O-Matic, 
Ltd. 


8DW5 


P.T.O. 


Rotary 





24" 


2" 


1.6 


© Schulte 


RS-H 
High Lift 


P.T.O. or 
Hydraulic 


Rotary 


2 to 3" 


28" 


2" 


2.4 


© Steinman Manu- 
facturing, Inc. 


#480 


Hydraulic 


Fixed 


2 to 4" 


10" 


2" 


1.2 


© Thomas Equip- 
ment, Ltd. 


Hopper 
Type 


Drawbar 


Fixed 


to 12" 


Not Available 


1 1/2" 


2.0 


© West Co 


A1H 


Drawbar 


Rotary 


Not Available 


24" 


2 1/2" 


1. 1 


© Wisconsin 

Rock Harvester 


HD 58 


P.T.O. 


Rotary 


2 to 4" 


500 lbs. 


1" 


1. 6 



LU,INLV (1) Potato Chain (2~) Rotating U.iki- (I) Rotating CiKje @ Passive Rake 



36 



TABLE 2 (Cont'd.) 
SPECIFICATIONS 



TINE 
ADJUSTMENT 


HORSE POWER 
REOUIRED 


SPEED OF 
OPERATION 


WEIGHT 


DUMPING 
HEIGHT 


LENGTH 


SWATH 


1979 PRICE 
(F.O.B. Factory) 


No 


10 


1 to 5 mph 


4700# 


V 6" 


13' 0" 


5' 6" 


$ 5,220 


Yes 


35 


to 4 mph 


3500# 


6 1 4" 


10' 0" 


8' 0" 


$ 2,895 


Not Available 


70 


Oto 5 mph 


2500# 


5' 0" 


13' 6" 


5' 0" 


$ 5,546 


Yes 


50 


2 to 4 mph 


6810# 


6' 0" 


33' 0" 


8' 0" 


$11,260 


No 


Not Available 


Not 
Available 


1500# 


13' 6" 


12' 0" 


5' 0" 


$ 2,200 


No 


60 


2 to 3 mph 


6000# 


2' 8" 


16' 0" 


4' 10" 


$ 8,135 


No 


60 80 


4 to 5 mph 


4250# 


6' 3" 


21' 4" 


8' 0" 


$ 6,837 


No 


45 


to 4 mph 


3830# 


6' 0" 


16' 0" 


8' 0" 


$ 5,978 


No 


45 


to 4 mph 


2800# 


7' 6" 


17' 0" 


6' 0" 


$ 2,565 


Yes 


7 


to 6 mph 


1500# 


4' 0" 


10' 0" 


6' 0" 


$ 3,340 


No 


250 


to 6 mph 


3750# 


12' 0" 


30' 0" 


10' 7" 


$25,000 


No 


125 


2 to 4 mph 


13,000# 


10' 0" 


34' 0" 


8' 0" 


$31,400 


No 


Not 
Available 


3 to 4 mph 


6900# 


8' 0" 


20' 0" 


20' 0" 


$ 9,897 


No 


50 


2 to 3 mph 


5000# 


8' 6" 


14' 4" 


5' 0" 


$ 7,600 


No 


30 


> 5 mph 


1350ft 


3' 4" 


12' 0" 


3' 6" 


$ 1,625 


No 


45 


to 8 mph 


2800# 


7' 0" 


20' 6" 


7' 7" 


$ 6,082 


No 


>40 


2 to 4 mph 


2510# 


6' 8" 


14' 3" 


8' 0" 


$ 3,459 


No 


60 


1 to 4 mph 


4850# 


8'-0" 


15' 0" 


5' 3" 


$ 6,200 



37 



The digging head can take two forms. It is normally either a fixed blade 
or a rotating rake. The fixed-blade pickup method uses a steel blade to lift £ 
layer of soil and rocks from the surface. Forward motion of the rock picker 
forces this material into the separation mechanism. The cutting depth is 
hydraulically variable on some models to permit adjustment while in operation. 
Soil conditions and operating speed affect the depth of penetration. In 
general, the deeper the cut, the slower the rock picker must travel to avoid 
overloading the separating mechanism. The fixed-blade pickup method is used 
by many models in conjunction with potato-chain, rotating-cage, or passive- 
rake separation modes. 

Rotating-Rake Rock Picker 

The rotating rake is generally best suited to surface and shallow rock 
picking. The rocks must be loose and free, or else the spring-loaded rake 
teeth will ride over them. As the rake turns, it lifts rocks up onto a screen 
which allows the soil to drop out while the rock is directed into a collection 
box. These machines require dry, vegetation-free soil since vegetation and 
damp soil bind the separation mechanism and make it inoperative. 

Rotating-rake rock pickers operate on the principle of a rotating, spring- 
loaded picking reel passing over a heavy grill-bar-type apron (fig. 2). The 
depth at which the leading edge bar of the apron runs through the soil is con- 
trolled hydraulically, on most models, from the tractor. The action of the 
reel teeth loosens the rock, helps to break up clods, and rapidly moves the 
rock back into the hopper. Manufacturers claim that continuous picking 



r 



Stone box 



Rotating rake 




ction 
ravel 



FIGURE 2. - Rotating-rake separation mode. (Adapted from Degelman Product literature.) 



38 



operation even during tight turns is possible. They also claim a speed range 
from 1 to 5 mph, depending on soil conditions. Self-cleaning action and very 
little jamming should be attained using rake rock pickers. The design of the 
aprons is generally such that, when used for surface work on pasture or sod, 
the machine will take all the surface rock with little tearing of the sod. 

Rotating-Cage Rock Picker 

The rotating-cage rock picker (fig. 3) does not penetrate the soil; rocks 
must be windrowed before this machine is employed. A rotating shaft pushes 
the rocks onto a conveyor belt that transfers them into the rotating cage. As 
the cage turns, tumbling rocks break up dirt clods, liberating soil particles 
that can fall through the cage openings and return to the ground. The inclined 
cage directs the rocks through the length of the cage to the rear conveyor, 
which deposits them into a storage hopper or following trucks. 

For best performance by this type of rock picker, the rocks should not be 
mixed with excessive amounts of soil and vegetation. The separation area of 
this machine is the smallest of the four types. If plant material is encoun- 
tered, it tends to clog the cage openings and reduce the available separation 
area even more. 

Passive-Rake Rock Picker 

Passive-rake rock pickers (fig. 4) are the least complicated of all the 
available rock pickers. Most passive-rake rock pickers have a fixed rake with 
adjustable tines. They are not designed to penetrate the soil more than a 
few inches. As the passive rake is towed behind a tractor, the rocks are 
maintained on the L-shaped tines, while the fine particles fall through. When 
the tines are full of rocks, the collecting head is hydraulically lifted and 
dumped into the rear storage hopper. For effective operation, the soil must 
be loose and dry. 



Rotating cage 




FIGURE 3. - Rotating-cage separation mode. (Adapted from Hurley Product literature.) 



39 




Direction 
of travel 



FIGURE 4. - Passive-rake separation mode. (Adapted from Leon Product literature.) 



Rock Rakes 



Another form of rock removal device is the rock rake. Table 3 lists 
the general specifications of some popular models. Rock rakes can be either 
dragged behind a tractor or pushed by a dozer. The dragged varieties are 
used for light-duty application and will not penetrate the surface. Dragged 
rakes only windrow surface rock and debris. Other methods must be used 
to pick up the windrowed material. 



40 



TABLE 3 

ROCK RAKE SPECIFICATION 
COMPARISON TABLE 



COMPANY 


MODEL 


HORSE 

POWER 
REQUIRED 


OPERATING 
SPEED 
(MPH) 


TINE 
SPAC 
(IN) 


PENETRATION 
(INCHES) 


WEIGHT 

(LBS) 


HEIGHT 


WIDTH 


PRICE 

( 1979 FOB 

FACTORY ) 


DRAG TYPE 


AUSTIN 
PRODUCTS INC. 


LITTLE RHINO 


55 HP 


0-6 


2 


DRAGGED ON 
TOP OF EARTH 


370 


3'-4" 


8'-0" 


$825 


BRILLION 
IRON WORKS 


LR-8 


30 HP 


0-5 


2 




455 


4'-6" 


8'-0" 


$854 


DEGELMAN 
INDUSTRIES LTD. 


ROCK RAKE 
W/BRUSH KIT 


50 HP 


3-5 


2 




3200 


3'-8" 


14-0" 


$4,860 


YORK MODERN 
CORPORATION 


R.E. 


25 HP 


2-6 


2 




425 


3'-2" 


8'-0" 


$1,550 


PUSH TYPE 


FLECO 
CORPORATION 


9-S 


USE WITH 
D-9 DOZER 


VARIES WITH 
EQUIPMENT 


12 


21 


10.520 


5'-4" 


13'-8" 


$18,100 


ROCKLAND 


FF-3 

FOR FIAT 

ALLIS 


USE WITH 

FIAT- ALLIS 

DOZER 




12 


20 


5,800 


5-8" 


11 '-6" 


$8,710 


ROCKLAND 


RF-3 
FOR CAT 


FOR D-9H 
DOZER 




11 


20 


7,500 


5'— 11" 


11'-11" 


$8,710 



The push-type rock rakes are attached to the front of a dozer. They can 
be effectively used to remove large rocks and vegetation from the soil. Again, 
since the rocks are not picked up, they must be pushed into a pile or burial 
pit. The tines on the rake are generally about 12 inches long. 

TOPSOIL ROCK CONTENT INVESTIGATIONS 



To explore the feasibility of transferring topsoil rock removal technol- 
ogy in its present state from its agricultural origin into surface mine recla- 
mation, nine representative mine sites were visited. Figure 5 shows the 
location of the sites visited. By sampling rock contents of soils before and 
after they were affected by mining, an indication of the need for incorporat- 
ing rock removal into the reclamation plans could be ascertained. In addition, 
the capability of current rock-picker technology to function in mining environ- 
ments was assessed. Each site chosen provided a unique combination of topsoil 
quality, topography, climate, and method of mining. Further considerations 
were made of the States that had rock limitation regulations. In addition, 
mines using rock removal devices to improve reclamation were sought to assess 
successes and problems. 

Each mine visit consisted of a discussion with mine operators of mining 
methods, availability of topsoil, overburden characteristics, reclamation 
equipment, amount of land reclaimed annually, average amount of time spent on 



41 



IDAHO 



WYOMING 




OHIO CH-5. 



VA,/\W 

CH-61 
H-3 JJ^CH- 

TENN 

•CH-J 
ALA 



DEL. 



LEGEND 



200 400 600 



CH-I CASE HISTORY 
• MINE 



SCALE IN MILES 
FIGURE 5. - Location map— mine visitation sites. 



reclamation each year, and any particular reclamation problems experienced at 
the mine. The operator would then provide a tour of the operation for a first- 
hand view of mining practices and rock content evaluation of the soils. 

Rock content was evaluated by digging small test holes and then separat- 
ing and weighing the rock and soil components. Assuming a maximum mechanical 
picking depth (for optimum rock removal operation) of 12 inches, the samples 
were examined in two stages. The percent by volume of rock to soil was 
calculated at to 6 inches and for 6 to 12 inches. Segregation of rocks from 
soil was made by considering all material that passes through a 1-inch sieve 
to be soil and all that is retained to be rock. Those rocks in excess of 
3 inches in their smallest dimension were weighed separately; however, in 
most cases this size fraction was a small portion of the total rock content. 
Test results for each mine are summarized in table 4. 



42 



TABLE 4 

TEST HOLE RESULTS 



MINE 
SITE 


ORIGINAL ROCK CONTENT (%) 


RECLAIMED ROCK CONTENT (%) 


HOLE DEPTH 


HOLE 
AVG. 


HOLE DEPTH 


HOLE 
AVG. 


0-6" 


6-12" (i) 


0-6" 


6- 12" (i) 


CH-1* 




















CH-2* 




















CH-3* 




















CH-4 


5 


10 


7.5 


5 


6 


5.5 


CH-5 











10(2) 


10(2) 


10(2) 


CH-6 


7 


13 


10 


9 


14 


11.5 


CH-7 


7 


12.5 


9.75 


9 


14 


11.5 


CH-8* 




















CH-9 


7 


10 


8.5 


5 


7 


6 



* DENOTES MINE SITES IN PRIME FARMLANDS 

(,) HOLE DEPTHS VARIED BETWEEN 8-12" DUE TO DIGGING 
DIFFICULTIES AND TOPSOIL THICKNESS 

(2) PRIOR TO ROCK PICKING STEP; AFTER PICKING IT IS 
RETURNED TO FOR ALL CATEGORIES 



43 



Sensitivity Analysis 

To determine the effects of incorporating a rock picker into the reclama- 
tion plans, a sensitivity analysis was performed on two of the mines visited. 
While keeping certain criteria constant and varying those items that would 
most likely fluctuate, sensitivity graphs were constructed. Criteria held 
constant throughout this analysis were 

1. 6-inch effective penetration depth of rock picker. 

2. 8-foot effective picking width. 

3. 5-mile-per-hour ground speed during dumping cycle. 

4. 60-second dump cycle. 

5. $30,000 cost for rock picker and tractor. 

6. 7-1/4-hour shifts. 

7. UMW operator for tractor (Grade 1). 

8. 90-percent availability of rock picker and tractor. 
Items considered as variable were 

1. Operating speed — 1 to 5 miles per hour. 

2. Hopper capacity — 4 to 16 cubic yards. 

3. Haul distance to dump — to 5,000 feet. 

4. Hopper versus direct loading. 

Each of the four variable items was graphed as a function of the percent 
of rock contained in the topsoil. These analyses of the relationship between 
the rock content of the topsoil and the horsepower required to remove that 
rock (expressed in horsepower-hours per acre) provide a visual display of the 
sensitivity of the reclamation effort to these variables. 

Horsepower-hour per acre units were chosen to portray the incremental 
increases in the rock removal effort as the rock content increased in order to 
provide a relationship of universal and timeless application. These units 
reveal the physical energy required to accomplish given tasks by summing the 
products of the total available potential flywheel horsepower outputs of all 
contributing pieces of equipment multiplied by the total hours over which 
they were applied. This figure is, in turn, divided by the number of acres 
reclaimed. These units can be converted to cost per acre in a single step, 
at any future point in time, by simply multiplying times a conversion factor. 



44 



Projected Rock Picker Efforts 

Table 5 presents the topsoil removal and reclamation efforts with proj- 
ected rock picker effort for all nine mine sites visited. Effort data 
obtained from the sensitivity analysis were used to compute the projected 
rock picker efforts at the other seven sites visited. Also included in 
table 5 are topsoil removal and reclamation efforts per ton of coal with and 
without the addition of a rock picker. Table 6 translates effort into costs 
based on 35 cents per horsepower-hour . 

TABLE 5 

TOPSOIL REMOVAL AND RECLAMATION 

EFFORTS WITH PROJECTED 

ROCK PICKER EFFORTS 



MINE 
SITE 


EFFORT 
WITHOUT ROCK PICKER 


PR0JECTEI 
WITH R0CI 


) EFFORT 
( PICKER 


H.R-HRS/ACRE 


H.R-HRS/TON 


H.R-HRS/ACRE 


H.R-HRS/TON 


CH-1 


44X00 


5.0652 


46.462 


5.0668 


CH-2 


72.700 


15.9942 


74.262 


15.9958 


CH-3 


35.100 


9.3535 


36X62 


9.3558 


CH-4 


123.100 


11.3315 


124X62 


11.3363 


CH-5 


7.500 


3X608 


9X62 


3.6761 


CH-6 


217.100 


15.5063 


218X62 


15.5175 


CH-7 


25.700 


11.4131 


27.262 


11.4247 


CH-8 


113.900 


16.0300 


115.462 


16.0312 


CH-9 


148.300 


30.2588 


149X62 


30.2695 


AVERAGE 


87.600 


13.1793 


89.151 


13.1860 



45 



TABLE 6 
TOPSOIL REMOVAL AND RECLAMATION EFFORTS 

WITH PROJECTED ROCK PICKER EFFORTS 



MINE SITE 


EFFORT WITHOUT 
ROCK PICKER 


EFFORT WITH 
ROCK PICKER 


PERCENT 
INCREASE 


CH-1 


1.77/ TON 


1.77/ TON 





CH-2 


5.60/TON 


5.60/TON 





CH-3 


3. 27/ TON 


3. 27 /TON 





CH- 4 


3. 97/ TON 


3. 97/ TON 





CH-5 


1.28/ TON 


1.29/ TON 


.78 


CH-6 


5. 43/ TON 


5. 43/ TON 





CH-7 


3. 99/ TON 


4. 00/ TON 


.25 


CH-8 


5.61/TON 


5.61/TON 





CH-9 


10. 59/ TON 


10 59/ TON 





AVERAGE 


4.61/TON 


4. 62/ TON 


.22 



CONCLUSIONS AND ENVIRONMENTAL IMPACT 

Rocks are a natural component of soil, yet at times they can be detri- 
mental to revegetation efforts. Large rocks hinder attempts to seed an area. 
A prevalence of rock on or near the surface retards the establishment of 
vegetative cover by restricting root growth and limiting moisture distribution, 

As a side effect of this impedance to vegetation, there will be an 
increase in the amount of sedimentation. Erosion, transportation, and deposi- 
tion of soil particles impair environmental quality. The source area is 
robbed of nutrient-providing soil, the transporting water becomes turbid and 
affects the aquatic life of the receiving stream, and the deposition can 
result in a clogged stream channel, lake, or pond, or in suffocation of produc- 
tive land. 

There can also be harmful effects on the wildlife from erosion and 
sedimention in the form of destruction of their refuge areas. These are 
often damaged or destroyed without being noticed, since they are remote from 
the "affected area." 



46 



Past mining practices led to mixing of consolidated and unconsolidated 
strata within the same spoil pile. In the process, the strata were inverted, 
making it impossible to replace the topsoil in its original condition. To 
alleviate the destruction of the natural soil conditions, States began requir- 
ing separate handling of the topsoil. 

The segregated removal, storage, and replacement of soil horizons during 
coal mining virtually eliminate the introduction of bedrock fragments into the 
reclaimed topsoil layer; thus the rock content should be unchanged and 
reclaimed areas should be of equal quality to their premining conditions. 
Recently, implementation of the Federal surface mine law forced the segrega- 
tion of soil horizons to be implemented nationwide. This practice has had a 
noticeable effect in States without previous rock content restrictions, where 
an extreme decrease in the contamination of topsoils by rocks is apparent. 

Although national implementation of rock pickers by the mining industry 
is neither necessary nor probable, for those instances when land use improve- 
ment is desired, a rock removal system may prove to be surprisingly cost 
effective. Of the currently available designs, the direct-acting rock pickers 
(figs. 1-3) — those that continuously loosen and sieve a layer of soil — perform 
better and more efficiently than cyclic-acting machines (fig. 4). Passive 
rakes often bounce off large rocks or force them deeper into the soil, and are 
thus less effective for rock removal. In addition, they are slower owing to 
the required stops for emptying the rake into the storage hopper and for 
dumping the storage hopper. These two nonproductive cycles of a three-cycle 
operation greatly limit productivity rates as compared to the continuous 
direct-acting types of rock pickers. 

For the operator who plans to improve the land use from its premining 
status, the employment of a rock removal system is effective and relatively 
inexpensive. The economic impact on both the small and large operators is 
slight, as shown by the previous sensitivity graphs and unit cost estimates. 
In terms of the cost versus benefit, any area whose land use has been improved 
will be more valuable than it was. The cost of utilizing a rock removal 
system that is properly sized for the volume of rock removal necessary can be 
more than offset by the increased land value. Surface mine operators with a 
vested interest in the properties they mine could be shown that, for a nominal 
investment of capital and effort, a sizable valuation increase could be 
derived. 

In areas where the former optimum land use was woodlands owing to an 
inherently excessive rock content, the use could conceivably be upgraded to 
grasslands. Likewise, in areas where cropland is scarce, a suitable substitute 
might be produced from previous grasslands or even woodlands. The most 
impressive cost-benefit results, however, would be in upgrading rocky waste- 
land into developable property. There are many minable areas with rocky 
or no topsoil and abundant bedrock outcrops. When these areas are mined, an 
increased amount of soil materials is produced. The utilization of a rock 
picker to decrease rock content would manufacture land of a quality that 
surpasses that of its surroundings for developmental purposes. 



47 



The financial advantage of a rock removal system begins even before the 
reclamation is completed on a severely rocky site. The removal of boulders 
and/or the reduction of the rock content can decrease the planting cost by 
permitting the mechanical preparation of a proper seedbed, mechanical tree 
planting, and improved revegetation success. Thus, the initial cost of plant- 
ing, as well as the probability of partial or total replanting (to meet the 
bond release requirements), will be reduced. 

In areas like the semiarid Southwest, where topsoil is of limited quan- 
tity and poor quality and is underlain by decomposed sandstones, the probabil- 
ity of successful establishment of vegetative cover may be improved by special 
rock reduction methods. The productivity of a reclaimed area might be improved 
by employing a machine that crushes the rock it engulfs and returns the reduced 
rock particles to the ground. If this type of rock reduction was applied to 
the upper subsoil layers, it would increase the amount of soil material, 
improve the availability of soluble minerals for plant nutrients, increase 
the moisture-retention capabilities of the root medium, and accelerate the 
development of soil horizons. 

A possible disadvantage of using rock pickers in the reclamation of 
surface mines would occur when the removal of rocks accelerates the erosion 
of restored slopes. Removal of the resistance to erosion that rocks provide 
may allow excessive gullying to occur. This disadvantage of rock removal 
could be eliminated by frequent terraces, or contour plowing, raking, or 
disking. These practices retard surface flow velocities, reducing the water's 
erosive power. 

Areas that are reclaimed for farming uses will experience the reoccurrence 
of rocks periodically, due to the combined effects of repetitive plowing 
patterns, siltation, and frost action. Plowing overturns the topsoil, and if 
the same plowing pattern is repeated year after year, the result is a lateral 
shift of soil, which is most pronounced on sloping ground. Siltation can 
carry away thin layers of topsoils, which decreases the rock cover. Finally, 
the frost action physically pushes rocks toward the surface. Separately these 
are minor factors, yet collectively they will allow rocks below the cleared 
level to migrate up into the tillage zone. This return of rocks will take 
varying amounts of time, depending on the depth of rock removal and the depth 
of frost penetration. Overall, the infiltration of rocks into the tillage 
area is extremely slow and is not a formidable problem; current restoration 
practices will provide a reoccurrence rate similar to that of adjacent, 
unmined lands of similar strata. 



48 



TRANSPLANTING NATIVE VEGETATION 

by 

Earl M. Frizzell, l James L. Smith, 2 and Kent A. Crofts 3 



INTRODUCTION 

Transplanting native vegetation (trees, shrubs, and other species) is a 
viable alternative for reclamation of surface-coal-mined lands. Transplanted 
native vegetation both provides mature growing plants immediately to the 
reclaimed area and creates a nucleus from which seeds and other organisms can 
reinvade the area. Transplanting also provides immediate cover for wildlife, 
can be used for erosion control, and improves landscape aesthetics of 
recontoured areas. The transplant system described in this paper, consisting 
of a front-end loader and a transporter, is intended to provide equipment with 
which transplanting can be accomplished effectively and efficiently with 
minimal costs since current mechanized transplanting systems are expensive as 
compared with reseeding or planting of nursery stock. 

Most of the current transplanting equipment has evolved from nursery and 
landscape applications and is not sufficiently durable for the operating 
environment and steep slopes encountered in surface mines. Further, with this 
equipment, it may be possible to move only one moderately sized plant at a 
time, and the removal operation generally destroys virtually all the vegetation 
around the plant. Other specialized pieces of equipment, although suitable for 
reclamation, have high acquisition costs, and since the reclamation period 
may be of short duration, restricted usage may make their purchase difficult 
to justify. However, if the reclamation equipment can serve as a backup to 
regular mine production equipment when not in reclamation service, economic 
analysis may show the investment justifiable. Examples of such equipment are 
tree spades and mechanical transplanters. 

FRONT-END LOADER STUDY / 

The front-end loader (FEL) is a piece of mine production equipment that 
has been used, on a limited basis, for transplanting native vegetation in 
surface mine reclamation. However, the FEL is expensive, in terms of both 
capital and operating costs. Therefore, if an FEL is used in reclamation, 
its functions and capabilities should be optimized to achieve maximum 
productivity during the time it is available. 

Conventional FEL buckets are designed to maximize the volume of material 
that can be loaded from piles or embankments. However, for transplanting, the 

^General engineer, Spokane Research Center, Bureau of Mines, Spokane, Wash. 
2 Professor of agricultural engineering, Colorado State University, Fort 

Collins, Colo. 
3 Manager of reclamation and environment, Energy Fuels Corp., Steamboat 

Springs, Colo. 



49 



FEL bucket should be designed to maximize the area of material Csoil plus 
vegetation) that can be removed. Further, because of operating costs and 
production efficiency, the FEL should be used only for removing clumps of 
vegetation from undisturbed soil and transporting them short distances to the 
transplanting area. 

Many mine reclamation operations require moving native vegetation several 
miles. Also, to maximize use of available vegetation, it may be necessary 
to remove clumps of vegetation and store them in a holding area for several 
weeks before they are moved to the transplant site. In these situations, the 
transplant system requires a transport capability in addition to the removal 
capability of the FEL bucket. The transporter should be capable of picking 
up several clumps of vegetation, moving them several miles rapidly, and plac- 
ing them on the ground at the transplant site. 

Transplant Bucket Operating Procedure 

Conventional FEL buckets are designed to load from piles or embankments. 
Therefore, they are deep and have relatively high sides, and the horizontal 
distance that the bottom extends beyond the bucket top is relatively small. 
When this type of bucket is filled with clumps of vegetation, this configura- 
tion disturbs taller plants such as trees, and after transplanting they may be 
crooked. 

The general design of the transplant bucket requires understanding the 
operating procedure used for transplanting. This procedure, which is markedly 
different from typical FEL operation, follows: 

1. A vertical bank or step, approximately 2 feet high, is cut around the 
source of trees and shrubs. This must be done with the front-end loader and 
transplant bucket. 

2. With the bucket bottom parallel to the ground surface and between 12 
and 24 inches below the top of the vertical bank, the bucket is pushed into 
the bank. 

3. When the bucket is full or driven to refusal, it is lifted vertically, 
thereby removing a clump of vegetation and soil. 

4. The bucket is tilted back (towards the loader) about 10° to 15°, and 
the clump is transported by the loader to the transplant or storage area. 

5. At the transplant area, the bucket is tilted forward (30° to 45° or 
more) and the loader is reversed, leaving the clump on the ground. 

6. The loader is returned to the source of vegetation, and the cycle is 
repeated. Any access roads that may be required for transplanting are 
constructed prior to picking up the next clump, and any necessary surface 
leveling is done. All roadbuilding and leveling operations must be done with 
the reclamation bucket. 



50 



Bucket Design Criteria 

The reclamation bucket design criteria follow logically from the above 
operating procedure. The criteria developed for the reclamation bucket are 

1. The force required to push the reclamation bucket into the soil bank 
was determined. To accomplish this, a series of "plate penetration tests" was 
conducted. The plate penetration apparatus consisted of a flat plate and a 
cutting edge, representative of a segment of the bottom of the reclamation 
bucket. The force required to push the plate into the soil bank was deter- 
mined as a function of the distance the plate was pushed into the bank. 

2. The tractive capability of a Terex 1 * model 72-71A FEL was obtained 
from the loader manufacturer and standard construction equipment resource 
information. A similar procedure could be used for any size or make of FEL. 

3. The size of the reclamation bucket was determined by matching the 
tractive capability of the FEL to the force required to push the bucket into 
the soil bank. 

4. The force required to lift the clump of vegetation vertically from 
the soil bank was determined and compared with the lift capability of the 
FEL as given in the manufacturer's specifications. 

5. The safe transport load for the reclamation bucket was determined 
from the manufacturer's specifications and standard construction equipment 
resource information. 

6. Soil must be held on the plant roots with minimal disturbance during 
loading and unloading. In this regard, a suitable liner or coating should be 
provided on the surface of the reclamation bucket to reduce friction and 
decrease the tendency for soil to stick. The latter problem becomes 
particularly serious in cold weather because of the tendency of soil to freeze 
to the surface of the bucket. Once a soil clod sticks to the surface of 

the reclamation bucket, it disturbs the clump of vegetation until it is 
physically removed. 

7. The force required to push a bucket into a soil bank can be reduced 

by mounting teeth on the cutting edge of the bucket. This was confirmed during 
the plate penetration tests. However, it is also necessary to confine soil 
in the clump of vegetation, particularly if the clump includes trees. Confin- 
ing soil in the clump is a problem if the clump is transported in the bucket. 
Teeth allow soil to fall out of the clump and were, therefore, not included 
on the initial bucket. 

Reclamation Bucket Specifications 

1. Size will be 15 feet wide, 5 feet deep, and 3 feet high. This size is 
within the operating capability of the Terex model 72-71A loader. 

Reference to specific equipment or trade names does not imply endorsement by 
the Bureau of Mines. 



51 



2. Lucite will be used to line the inside bottom of the reclamation 
bucket. This material proved superior in field tests and will significantly 
reduce the sticking problem and problems of soil freezing to the bucket. 

3. The front cutting edge of the reclamation bucket will be straight and 
balanced (the cutting edge will have an equal angle and length bevel on top 
and bottom) . This will aid in controlling the depth of cutting and help con- 
fine soil in the clump. 

TREE CLUMP TRANSPORTER 

Analysis of the FEL vegetation clump transplanting operation indicated 
two factors as limiting the operation. The first was that the FEL was very 
efficient in removing clumps and planting them, but was relatively inefficient 
as a means of transportation, particularly if the distance was more than 300 
yards. The second limitation was that some mines may not have an FEL available 
when needed for the transplanting operation. The FEL is a very common piece of 
production equipment in surface mines, but the total time an FEL was available 
for transplanting might be relatively small. 

These problems can be solved by including a separate transporter in the 
transplant system. The vegetation clump transporter must pick up clumps of 
vegetation removed from undisturbed premined land by an FEL, transport the 
clumps, and place them in a transplant area. Proposed design criteria for the 
transporter are 

1. Capable of picking up clumps of vegetation, each having an area of 
75 square feet, and including small trees. 

2. Capable of transporting approximately 200 to 300 square feet of 
vegetation clumps per load at speeds up to 20 miles per hour. 

3. Capable of placing the vegetation clumps in the transplant area 
either as individual clumps or as groups of clumps up to the total area on 
the transport. 

A used Hesston stack mover is presently being modified and tested to 
evaluate the functions required for the transporter. The machine was origin- 
ally manufactured to load, transport, and unload haystacks. It consists of 
the follwoing mechanical elements: 

1. A tilt-bed trailer having a surface area of approximately 170 square 
feet. 

2. A chain conveying system capable of sliding the stack across the top 
of the trailer. 

3. A pickup roller for separating the stack from the ground. 

4. A set of tracks located at the rear of the trailer to pull the 
trailer under the stacks. 



52 



The rear tracks are synchronized with the conveyer so the stack is pulled 
up into the trailer at the same rate the tracks pull the trailer under the 
stack. When unloading, the stack is moved off the trailer at the same rate 
the rear tracks push the trailer forward. The maximum tilt angle of the 
trailer is approximately 15° (about 20 percent of the angle used between the 
FEL transplant bucket and the ground surface when unloading) . When the clumps 
of vegetation are handled by the transporter, they are subjected to minimal 
bending, and the plant survival rate should be satisfactory. 

The stack mover was converted to a vegetation transporter by the 
following modifications: 

1. The subframe and tilt bed were strengthened for increased load- 
carrying capability. 

2. The pickup roller was removed, and a short incline was located on the 
tail of the trailer to slide the vegetation clumps up on the conveyor chain. 

3. The tilt-bed trailer was covered with Lucite to reduce friction and 
facilitate moving vegetation clumps across the top of the trailer. 

4. A self-contained hydraulic system was mounted on the trailer, so only 
a prime mover (truck or farm tractor) will be required for operation of the 
transporter. 

It should be noted that although the converted stack mover is narrower 
than the transplant bucket (9 feet compared to 15 feet) , it will be possible 
to move clumps having the full 5-foot lateral dimension of the transplant 
bucket. This is the critical dimension, since it represents the length over 
which the clumps are subjected to bending as they are moved on and off the 
transporter. 

In the final design concept, the vegetation clump transport system would 
be operated as follows: 

1. An FEL would be used for a short time to remove a large number of 
clumps of vegetation from the undisturbed premined land and store them 
conveniently nearby. The FEL would then be free to return to mine production 
activities. 

2. The transporter would pick up the stored clumps of vegetation, move 
them to the transplant area, and place them on the ground. 

FIELD DEVELOPMENT TEST 

During the growing season of 1980, a developmental test of the vegetation 
clump transplant system will be conducted to study its effectiveness. Field 
test studies will be conducted in the following areas : 

1. Survival rate by species. 



53 



2. Growth rate by species. 

3. Survival of species as affected by the time of year transplanted. 

4. Equipment operating efficiency and costs. 

5. Provision for wildlife cover in transplant areas. 

6. Buildup of moisture in transplant areas due to retention and buildup 
of snowpack. 

7. Provision of ground cover and/or erosion control in the transplant 
areas. 

8. Cold weather transplanting procedures. 

9. Method analysis to reduce number and/or complexity of operations. 

The prime contractor for the field test is Colorado State University, 
Fort Collins, Colo. The cost-sharing cooperator is Energy Fuels Corp. , which 
will provide senior staff, machinery, equipment, and facilities for evaluation 
of the tree transplant system. Field test development will be conducted at the 
Energy Fuels Corp. mine, near Steamboat Springs, Colo. 

SUMMARY 

Advantages of the complete transplanting system, including the transplant 
bucket and transporter, are 

1. Native vegetation can be moved efficiently and economically over 
longer distances, perhaps several miles, than is possible with the FEL alone. 

2. An FEL, a piece of conventional mine production equipment, would be 
readily available but would be used only on a limited basis so as not to impede 
production activities. 

3. The transporter could be used continuously without interfering with 
mine production. Larger areas could be thus transplanted in the same time 
period. 

4. Native vegetation could be removed from an unmined area, placed in a 
holding area by the FEL, and moved by the transporter to the transplant area 
when convenient. This will allow maximum productivity with the FEL when it is 
available and provide increased flexibility in scheduling the FEL. 

5. The transporter would be lower in initial cost than an FEL and less 
expensive to operate. Transplanting costs would therefore be reduced. 

6. A truck, large farm tractor, scraper tractor, or other piece of reclama- 
tion equipment, not directly required for mine production, could be used to pull 
the transporter. All power for the transporter operation other than mobility is 
self-contained, so the prime mover could be changed easily. 



54 



SELECTIVE OVERBURDEN PLACEMENT 

by 

Gregory G. Miller 1 



INTRODUCTION 

The Bureau of Mines sponsored a study of selective overburden handling at 
a coal mine in Colstrip, southeastern Montana. The Montana Agricultural Experi- 
ment Station in Bozeman, Mont., performed the work. They determined a recom- 
mended drilling intensity needed to accurately identify salt and trace metal 
materials that would be inhibitory to plant growth and performed a selective 
handling demonstration. 

DRILLING INTENSITY 

Current practice of identifying toxic ions of salts and trace metals 
involves drilling on a 1-mile grid in unfaulted areas and on a 1/2-mile grid 
in faulted areas. This guideline is based on a commonly accepted assumption 
that if inhibitory materials are present, they will be located in a physio- 
chemically uniform geologic strata. Consequently, if an inhibitory zone is 
found, selective overburden handling of this single strata is necessary. To 
evaluate this guideline, 300 boreholes were drilled on an approximate 150-foot 
grid over a 100-acre premine site. Samples were taken on 5-foot intervals, 
and approximately 100,000 separate physiochemical laboratory tests were per- 
formed at a mobile laboratory at the mine site. 

Data on the physiochemical properties at the site were graphed showing a 
three-dimensional distribution of each parameter. Figure 1 is a three- 
dimensional view of the distribution of clay at the site where the first four 
dragline passes would occur. This diagram and other diagrams of soluble salts, 
lead, and nickel show that inhibitory physiochemical parameters are distrib- 
uted in overburden zones independent of the geologic strata and generally 
independent of each other. It was also determined that the horizontal extent 
of the toxic zones was considerably less than 1 mile, indicating that the cur- 
rent guideline is not effective. To detect each parameter at a 90-percent 
accuracy level required an overburden drilling grid of 100 to 200 feet, con- 
siderably less than the guidelines suggest. 

Therefore, to properly identify inhibitory material, a two-step drilling 
program is proposed. First, the overburden should be drilled on a 1/2-mile 
grid. This would identify which physiochemical parameters exist in inhibitory 
concentrations. Then the site should be drilled on a 100- to 200-foot grid to 
identify the vertical and horizontal extent of those parameters determined to 
be present in inhibitory concentrations. This two-step procedure will reduce 
the costs of laboratory analysis by eliminating repeated analysis of parameters 



Mechanical engineer, Spokane Research Center, Bureau of Mines, Spokane, Wash, 



55 




100 

Scale, meters 



FIGURE 1. - Three-dimensional view of clay distribution. 



found in step 1 to be insignificant. Another conclusion is that, generally 
speaking, mines that selectively bury a certain strata based on a drilling 
grid identification in the thousands of feet are likely to entirely miss 
considerable zones of inhibitory material. 

INHIBITORY MATERIALS 

In the Western States, inhibitory materials contain concentrations of 
salts and trace elements. Salts of calcium, magnesium, and sodium associated 
with sulfates (SO^) and carbonates (HCO3) are present. Trace metal ions of 
nickel, cadmium, zinc, molybdenum, and lead were a problem at the study site, 
and levels of copper, manganese, mercury, selenium, and boron should be checked. 
Suspect levels of pH, ammonium, sand, and clay were found at the site. 

High concentrations of salts adversely affect plant-water relationships 
by upsetting the plants' osmotic pressure. High concentrations of trace 
metals cause metabolic interference in plant cell physiology. Spoils contain- 
ing more than 40 percent clay prevent plant root penetration and water infil- 
tration. Clays are usually associated with high levels of positive trace 
metals ions which cling to negatively charged clay. Spoil containing more 
than 70 percent sand retains little water or nutrients essential to plant life. 
Drinking water contaminated with salts and trace metals causes metabolic prob- 
lems in animal life. 



56 



THE LEACHING PROCESS 

Leaching takes place if the spoil water begins to flow by gravity, carry- 
ing with it soluble constituents of the spoil. The water content must be 
above the field capacity for leaching to be significant. The field capacity 
is the amount of water held in the spoil after excess water has drained away 
and the rate of downward movement has substantially decreased. Leaching is 
most significant as the water content approaches saturation. 

It is desirable to suppress the leaching process in the presence of spoil 
containing inhibitory concentrations of trace metals or salts. This may be 
done in four ways: (1) The inhibitory material can be sealed with an imper- 
meable layer; (2) the inhibitory material can be diluted through mixing; 
(3) a topographic dome can be made above the inhibitory material to divert 
surface water away; and (4) subsurface water can be consumed by plantlife. 
Clay seals and dilution were investigated in this project. 

CLAY CAPPING 

Figure 2 shows selectively handled inhibitory material that was buried 
and capped with clay. It is desirable to use spoil located at the mine as a 
source of clay to reduce haulage costs. A clay cap intended to divert water 
is constructed with spoil dominated by a smectite clay. Smectite clay has a 
2:1 lattice structure of a tetrahedral-octahedral-tetrahedral arrangement. 
Two-to-one lattice clays do not have a hydrogen bonding effect, so the units 
can readily expand and contract with wetting and drying, creating a formation 
that tends to be impermeable when wet. If the clay source is dry, it must be 
irrigated to achieve an optimal moisture content of 14.6 percent by weight. 
The clay should be laid over the inhibitory zone with scrapers. The scrapers 
should also attempt to compact the clay to a standard Proctor density of 
112 pounds per cubic foot. The cap should be formed with a 5:1 grade in all 
directions to create an umbrella effect to shed percolating water. The clay 
cap should be thick enough so that it will not rupture when the dragline 
spoils overburden on it. 

A 60-cubic-yard dragline was able to build the foundation material and 
selectively place saline inhibitory material for capping. This was performed 
on approximately two-thirds of an acre and 14,000 cubic yards of a saline 
material were buried. The saline material was originally located in the top 
15 feet of the overburden. The stripping ratio was 3:1. The cost of the 
operation was 50 percent more than normal dragline operations. 

The cost and complexity of selective overburden handling rest on whether 
the inhibitory materials are at the top, middle, or bottom of the overburden 
profile, and on the availability of clay. More efficient selective over- 
burden handling procedures could significantly reduce costs. 

The inhibitory overburden material should be buried deep enough to pre- 
vent future contact with the surface environment caused by man or nature. If 
the mine has interrupted an aquifer, the material should be buried above the 
predicted reestablished aquifer. The new aquifer capillary fringe must not 



57 



\ \ 



0? f RFVEGETATED SLOPED SURFACF 



I 




*'*0, 



IT? 



/ ^SATURATED FLOW 

SPOIL 



MPERVIOUS 
CLAY CAP 




WATER TABLE 

I I I I I I I I I I I I I 







■U.LUJJJJJJ.J.J.mU.mL.Um.i. 



/CAPILLARY FRINGE 

■ I..L.U...U I .L.L.U..I 



.SATURATED ZONE OF RE-ESTABLISHED AQUIFER 



CONFINING STRATA 



FIGURE 2. - Infiltrating water is diverted by clay cap away from the inhibitory material. 



intercept the buried inhibitory material. (The capillary fringe is a zone 
above the new aquifer into which unsaturated water enters due to capillary 
rise.) If the capillary fringe intercepts the inhibitory material, fluctua- 
tion of the water table level causes a corresponding fluctuation in the capil- 
lary fringe. When the aquifer level drops, the fringe drops. When it later 
rises, the chemical constituents are now in the aquifer zone. The fringe can 
then carry dissolved chemical constituents with it. 

Because of the semiarid climate at the site after 2 years, unsaturated 
flow of water through the spoil has not been enough to evaluate the effective- 
ness of the clay cap. However, a small (50-foot-diameter) experimental cap 
was also built which could be flooded with water to determine its effective- 
ness in shedding the downward flow. Over a period of 2-1/2 months, about 
9-1/2 feet of water was applied in a diked area above the cap. This water 
application rate was extremely intense in comparison to the amount of water 
normally expected from precipitation. The change in the water content above 
and below the clay cap was monitored. The wetted front mushroomed out 



58 

laterally over the cap. Although the cap Itself became quite wet, the inhibi- 
tory material beneath it never reached saturation. The cap was determined to 
be an effective barrier to saturated flow. 

DILUTION OF INHIBITORY MATERIALS 

Mixing of inhibitory spoil material with other "clean" spoil tends to 
dilute the concentration of inhibitory material to acceptable levels. Mixing 
can be performed three ways with a dragline through digging and spoiling. 
First, when an inhibitory zone intersects the digging face, the dragline can 
drag the bucket at an incline, mixing clean and inhibitory material. Second, 
the dragline can dump the spoil as it swings, spreading and thus mixing the 
material. Third, the dragline can dump on spoil peaks, causing mixing as 
spoil rolls down. 

Three types of dragline spoiling techniques were investigated: normal, 
dump, and scatter. Normal spoiling with a 60-cubic-yard dragline with a 
325-foot boom generally results in a bucket load of material being cast over 
an area 65 feet long by 35 feet wide. This was found to be true for several 
dragline operators, although their styles differed. Dump spoiling is used for 
initial spoiling on the pit floor. This involves stopping the dragline swing 
before dumping the load. It is used to avoid entrapments of pit water in the 
spoil because entrapped water causes subsidence and slope failure. Dump spoil- 
ing covers an area 35 feet square. Scatter spoiling involves dumping the load 
on the swing. The material is cast over a large area about 130 to 200 feet 
long. Scatter and dump spoiling increase cycle time. Three volumes of spoil 
were created with each method. Dump spoiling generally results in less mixing 
of inhibitory zones, and the technique should be used only when necessary. 
Scatter spoiling seemed to produce the best degree of mixing; however, normal 
spoiling could not be judged to be significantly different. 

Analysis of the resultant spoil yielded the following conclusions. When 
the inhibitory material constitutes less than 5 percent of the total overburden 
volume, the inhibitory zone was diluted to acceptable levels. When the inhibi- 
tory zone constitutes 5 to 15 percent of the overburden volume, only partial 
dilution occurs. When the inhibitory material exceeds 15 percent, only a 
small portion is diluted. In this case, selective overburden placement is 
necessary. No mixing occurs if the inhibitory material is spread throughout 
the entire overburden. 

Additionally, surficial overburden material may not be mixed as well as 
subsurface material. This may be due to a tendency to spoil surface materials 
onto the pit base in a dumping fashion, whereas deeper overburden materials 
are often cast normally or scattered over a larger area and slide down an 
existing spoil pile. 

It is always preferable to mix clays and sands . Although mixing of inhib- 
itory concentrations of trace metals and salts will increase the surface area 
available for deep leaching, mixing reduces the amount of inhibitory material 
in the plant root zone and the amount of inhibitory material available for 
leaching in the reestablished aquifer zone. 



59 



GROUND WATER 

Because of the limited depth of surface strip mining, only the shallow 
ground-water system was studied. Three aquifers were present in this system. 
The first is located in the permeable sandstone portion of the overburden, and 
the other two in the two coal seams. The second coal seam was not mined. Its 
aquifer was confined, and research found that surface strip mining has little 
effect on it. The top two aquifers were disturbed by mining, significantly 
affecting their level and direction of flow. A fourth aquifer now exists in 
the shallow ground-water system located in the spoils. How and where this new 
aquifer forms will impact water supplies down gradient. Water availability in 
this semiarid region is critical to local agricultural activities. 

The spoils aquifer should be constructed of pervious , uncontaminated 
material so that leaching of soluble salts and trace metals will not take 
place. Wells placed in the spoil confirm that the new spoils aquifer is form- 
ing and is exibiting confinement characteristics similar to those that exist 
in the unmined coal seams . 

A network of monitoring wells were placed in the overburden and spoil. 
Water levels and water quality measurements were taken. Data suggest that 
mining activities have had little effect on the overburden water levels at 
distances greater than 2,000 feet from the mine pit. This may be due, in part, 
to variations in lateral hydraulic conductivity, lack of sufficient time for 
adjustment to new conditions created by continued mining, and greater amounts 
of precipitation during the monitoring period. The top coal seam water level 
was reduced up to 1 mile from the mine pit. The water level tended to drop 
more in the coal seam aquifer than in the overburden aquifer. This seems to 
be due to the relatively continuous and homogeneous nature of the coal seam 
and the highly discontinuous and heterogeneous nature of the overburden. Con- 
sequently, dewatering of the coal seam is evident at a greater distance from 
the mine pit than is dewatering of the overburden aquifer. 

Surface water from streams, ponds, impounded water, and the mine settling 
ponds can be expected to be a source of recharge of the aquifers. The mine 
hydrologist must gather enough data to estimate the aquifer level in the spoil. 
This estimate is used in specifying the depth an inhibitory material can be 
safely placed. 

A comparison of 1923 water quality data with 1973 analyses indicates that 
no major changes in water quality have occurred owing to commercial mining at 
the site. Our analyses of water quality coming from the new spoil squifer 
indicate the water is generally more mineralized and of higher salinity. 

Mining altered the ground-water flow pattern in the overburden and coal 
towards the pit. However, this change in flow direction will cease once 
mining in the area has been completed and the spoil recharge is complete. 



60 



PREMINING HYDROLOGIC CONDITIONS OF FIVE SOUTHEASTERN OHIO WATERSHEDS 

by 
Gary E. Mcintosh 1 



INTRODUCTION 

The Bureau of Mines is currently sponsoring a research project in east- 
central Ohio to study the effects of surface mining of coal on ground and 
surface water. In Appalachia, land is being disturbed by surface mining at an 
accelerating rate to obtain coal for electric power production and other uses. 
Such mining may have profound effects on runoff, erosion, and water quality 
in a watershed. 

Strip mining may bring changes in the hydrology of surface-mined areas in 
two interrelated phenomena: flooding and sediment transport. Barren spoil 
areas and decreased infiltration rates tend to increase peak flow rates of 
runoff from mined areas. Such increased runoff erodes the spoil areas and 
carries spoil particles that cause sedimentation of waterways and reservoirs. 
Until spoil areas become stabilized with vegetation, significant quantities of 
sediment will continue to be transported. 

In addition, Federal and State governments have passed laws that require 
minimizing the disturbance to an area being mined and reestablishing the 
hydrologic integrity of a mined area. The Surface Mining Control and 
Reclamation Act of 1977 also requires that the mining company shall make a 
"determination of the probable hydrologic consequences of the mining and 
reclamation operations, both on and off the mine site, with respect to the 
hydrologic regime." The law states that if there is not enough information 
to make this determination, no mining permit will be granted. 

Because of the need for more knowledge on how a surface mine affects its 
surroundings, the Bureau of Mines has established a study with the U.S. Depart- 
ment of Agriculture - Science and Education Administration - Agricultural 
Research (USDA-SEA-AR) and the Ohio Agricultural Research and Development 
Center (OARDC) to 

1. Obtain and analyze hydrologic and water quality data from four treat- 
ment watersheds, 30 to 60 acres in size, scheduled for mining of different 
coal seams. Obtain and analyze hydrologic and water quality data from erosion 
and treatment plots and a control watershed. 

2. Characterize the study watershed and plots, and obtain physical and 
chemical data for the soils and overburden materials prior to surface mining 
and for the replaced topsoil and underlying spoil material following surface 
mining. 



Geologist, Denver Research Center, Bureau of Mines, Denver, Colo, 



61 



3. Describe the hydrogeology of the watersheds and the water quality 
characteristics of the aquifer systems before and after surface mining, and 
develop or adapt a ground-water model for simulations of the ground-water flow 
conditions and movement of solutes before and after surface mining. 

This research program was started in January 1976, and completion is 
planned for January 1983. This paper deals with the premining hydrologic 
conditions of the watersheds. 

MONITORING PROGRAM 

Five watersheds, ranging in size from 29 to 52 acres, were selected to 
study the effects of mining and reclamation on hydrology and water quality. 
Four of these watersheds will be mined, and one will be left in its natural 
state and used as a control watershed. All the watersheds are located in 
east-central Ohio (fig. 1), and are numbered in accordance with surface- 
minable coal seams. The study watersheds in Coshocton County (C06 and A06) 
and the one in Muskingum County (M09) are located in the Muskingum River 
basin. The two Jefferson County Sites (Jll and J08) drain into small tribu- 
taries of the Ohio River. 

On each watershed soil and vegetation surveys were run, and geologic 
cores were obtained in order to determine baseline physical conditions. 
Weather stations were set up to monitor precipitation (quantity and quality) , 
temperature, relative humidity, wind speed, and solar radiation. 

Infiltration tests are being run throughout the project , on all watersheds, 
to determine how infiltration capacity changes from premining to postmining 
conditions. 

Surface water quantity and quality measurements are being taken by the 
use of H-flumes, drop-box weirs, a broad-crested V-notch weir, a Parshall 
flume, a cashocton vane, and check ash samplers. Composite sediment samples 
are also being collected from runoff and base flow events. 

Ground-water conditions are being determined with gologic coring, an 
observation well network, and pump and slug tests. Ground-water quality 
samples are collected quarterly. 

In addition to the monitoring of the watersheds, erosion and treatment 
plots have been set up at three of the mine sites. The erosion plots were 
installed on four different slopes, and with four different lengths on the 
slopes. The treatment plots (10 at each mine) consist of standard plots on a 
9-percent slope, with treatments of different depths of topsoil and different 
mulching rates. The information from these plots will be useful for develop- 
ing criteria for diversion spacing and for establishing erodibility factors 
for soil loss prediction equations. 



62 








H 



Jefferson Co. 



A. Appalachian Exp. Ws. -> 



Coshocton Co. >1 A06 
Muskingum Co. 
Columbus 



Zaneville -"' 




V C06 



M09 



*\^ 




c '^-- 



V 



<~\ j 



N 



/ 



10 20 30 40 
I I I L__J 

Scale, miles 



FIGURE 1. - Location of study sites. 

RESULTS FOR PREMINING INVESTIGATIONS 

The periods of premining record for each watershed, and for each parameter 
for a watershed, varied as instruments were installed and mining progressed. 
The premining records for C06 and M09 cover less than 1 year. The end of the 
premining phase occurred when the watershed hydrology was changed by tree 



63 



removal and roadbuilding prior to mining. The Jll site has not yet been 
mined, and the A06 control site will not be mined, but an aribtrary cutoff 
date of December 31, 1977, was made for all the premining data included in 
this report. Because J08 has not been completely instrumented, its premining 
period has not begun except for collection of some ground-water data. Data 
on air temperature, relative humidity, wind, and solar and net radiation 
collected at the Jll site, however, can be extrapolated to J08, since the 
sites are only about 5 miles apart and variations over short distances are 
expected to be minimal for these parameters. The parameters which were 
analyzed from the surface water, precipitation, and ground-water samples 
are listed on page 64. 

Watershed C06 

The premining condition of watershed C06 (fig. 2) is characterized by 
an ephemeral stream 2,000 feet long. The maximum elevation is 1,075 feet, 
and the minimum elevation is 930 feet. The watershed has an area of 52 
acres, with a southeast aspect. 



Eight soil types, constituting 26 soil delineations, were mapped in the 
watershed. Five of the most extensive and representative soils - Johnsburg, 
Gilpin, Dekalb, Coshocton, and Monogahela - were sampled, and complete 
descriptions and characterization data were obtained. In general, these 
soils have favorable rooting depths and medium to high water-holding 
capacities. Most of the soils analyzed, except the Dekalb, would provide 
good material for topsoiling. 







LEGEND 
Natural spring 
Instrument plot 
Spring development 
Buried pipeline 
Core site 

Well monitoring the 2nd aquifer 
Sediment pond 
Gaging standard 
Watershed boundary 
Contour line 
Coal outcrop 
Access tube 







FIGURE 2. - Premining topographic map of watershed C06 showing instrumentation sites. 



64 



Parameters for Which Samples Were Analyzed 



Parameters for 
Sediment Fraction 
for Surface Water 



Parameters for 
Surface Water 



Parameters for Ground Water 



Aluminum 

Cadmium 

Calcium 

Copper 

Iron, total 

Lead 

Magnesium 

Manganese 

Mercury 

Nickel 

pH 

Phosphorus , 

total 
Sodium 
Strontium 
Sulfate 
Total organic 

carbon 
Zinc 

Parameters for 
Precipitation 

Aluminum 

Antimony 

Barium 

Bicarbonate 

Cadmium 

Calcium 

Copper 

Hydrogen sulfide 

Iron 

Lead 

Magnesium 

Manganese 

Nickel 

Nitrate (N) 

pH (laboratory) 

Phosphorus 

Silver 

Sodium 

Specific 

conductance 
Strontium 
Sulfate 
Zinc 



Acidity 

Alkalinity 

Aluminum 

Ammonia (N) 

Antimony 

Arsenic 

Barium 

Bicarbonate 

Cadmium 

Calcium 

Carbon dioxide 

Chloride 

Chromium 

Color 

Copper 

Cyanide 

Flow rate 

Fluoride 

Hardness 

Hydrogen sulfide 

Iron 

Lead 

Magnesium 

Manganese 

Mercury 

Nickel 

Nitrate (N) 

pH (field) 

Phenols 

Phosphorus 

Selenium 

Silver 

Sodium 

Solids, suspended 

Solids, dissolved 

Strontium 

Sulfate 

Temperature 

Zinc 



Alkalinity, as 

CaC0 3 
Aluminum, total 
Antimony, total 
Arsenic, total 
Barium, total 
Bicarbonate 
Cadmium, total 
Calcium, dissolved 
Carbon dioxide 
Carbon, total 

organic 
Carbonate 
Chloride, 

dissolved 
Chromium, total 
Color 

Copper, total 
Cyanide 
Fluoride, 

dissolved 
Hardness , 

noncarbonate 
Hardness, total 
Hydrogen sulfide 
Iron, dissolved 
Iron, total 
Lead, total 
Magnesium, 

dissolved 
Manganese, 

dissolved 
Manganese, 

suspended 
Manganese, total 
Mercury, total 
Nickel, total 
Nitrogen, NH^ as N 

total 
N0 2 + N0 3 as N 



pH (field) 
Phenols 
Phosphorus, total 

as P 
Phosphorus, total 

Potassium, dissolved 
Residue, dissolved 

(calculated sum) 
Residue, dissolved 
Sodium absorption 

ratio 
Selenium, total 
Silica, dissolved 
Silver, total 
Sodium, dissolved 
Sodium (percent) 
Specific conductance 

(field) 
Strontium, total 
Sulfate, dissolved 
Water temperature 

(° C) 
Zinc, total 



65 



The vegetation on the watershed consisted mainly of deciduous trees. 
The site had poor species composition and growing conditions. Major species 
are aspen, dogwood, black cherry, maple, red oak, and musclewood. Ground 
cover was also quite variable. Average ground cover values for herbs, woody 
vegetation, duff, and bare soil and/or rock are 32, 14, 38, and 16 percent, 
respectively. 

The precipitation record spanning the C06 watershed premining period was 
from December 6, 1975 through November 3, 1976. The total precipitation for 
the period of record was 40.37 inches, with snowfall accounting for 2.79 
inches. The most extreme event during the premining phase occurred on 
July 8, 1976, when the rainfall totaled 1.65 inches. The peak intensity of 
this event was 5.16 in/hr for 5 minutes — totaling 0.43 inch. The highest 
2-hour intensity during this event was 1.60 in/hr, approximately a 5-year 
precipitation event. 

Infiltration tests were run on the watershed on the Coshocton, Gilpin, 
and Dekalb soils. At application rates of 2.0 and 2.5 inches per hour, 
equilibrium rates of 0.56 and 1.25 inches per hour were reached in about 3 
and 4 hours for the Coshocton and Gilpin soils, respectively. The data for 
the Dekalb are considered questionable. 

A spring was developed on the watershed at the coal outcrop. The minimum 
flow was 0.003 cubic foot per second (cfs) , and the maximum was 0.012 cfs. 
The spring's range of average daily flow was 0.003 to 0.052 cfs. 

Mining commenced on watershed C06 before a full year's water quantity 
and quality data were obtained (data for the fall are missing) . The total 
surface flow for the period of record (1-1-76 to 11-3-76) was 33.54 inches. 
The peak event of 5.86 cfs occurred on July 7-8, 1976, with the causative 
precipitation totaling 2.39 inches. 

Base flow water had average concentrations of 183 yg/1 iron, 102 yg/1 
manganese, and 247 mg/1 suspended solids, and an average flow rate of 0.44 
cfs. The runoff water had average concentrations of 209 yg/1 iron, 97 yg/1 
manganese, and 870 mg/1 suspended solids, and an average flow rate of 
2.13 cfs. 

Ground-water levels indicate that the ground-water divide for both the 
top and middle aquifers at C06 coincides with the surface drainage divide. 
The top aquifer is above the clay that underlies the No. 6 coal. The middle 
aquifer is above the clay that underlies the No. 4 coal. Water in the deep 
aquifer moves northward; the top of this saturated zone is 30 to 100 feet 
below the middle aquifer. 

Water in the top aquifer is mostly of the calcium bicarbonate type. 
Specif ic-conductance values indicate that dissolved-solids concentration in 
parts of the middle and deep aquifers exceed the Environmental Protection 
Agency's recommended limit of 500 mg/1. Concentrations of dissolved iron and 
manganese commonly exceeded the recommended limits of 0.3 and 0.05 mg/1, 
respectively. Concentration of dissolved cyanide exceeded the recommended 
limit (0.01 mg/1) in one sample. 



66 



Watershed M09 

The premining condition of watershed M09 (fig. 3) is characterized by a 
continuously flowing stream 1,800 feet long. The maximum elevation of the 
watershed is 1,165 feet, and the minimum elevation is 933 feet. The watershed 
has an area of 43.5 acres, with a south-southeast aspect. 

Fourteen soil types, constituting 33 soil delineations, were mapped in 
the watershed. Five of the most extensive and representative soils — Lowell, 




200 

J 



Scale.feet 

LEGEND 
Instrument plot 
Spring development 
Core site 

Well monitoring the 2nd aquifer 
Sediment pond 
Gaging standard 
Watershed boundary 
Intermittent streams 
Contour line 
Coal outcrop 
• Access tube 

FIGURE 3. - Premining topographic map of watershed M09 showing instrumentation sites 



67 

Upshure, Wellston, Tilsit, and Brookside — were sampled, and complete descrip- 
tion and characterization data were obtained. In general, these soils have a 
high available-moisture-holding capacity. The texture, cation exchange 
capacity, and base status make these soils well suited for plant growth, 
except where there is a high clay content near the surface. With the excep- 
tion of the Upshur mapping unit and other areas where high clay contents are 
found near the surface, the soils of the watershed would be very good for 
topsoiling. 

The vegetation on the watershed consisted mainly of pasture species. 
Woody species occurring on the site included sycamore, tulip poplar, elm, red 
maple, red oak, white oak, and dogwood. Approximately 77 percent of the 
ground area was covered with a mixture of grasses and broadleaf herbs, and 
8 percent with woody vegetation; the remaining 15 percent was bare and/or 
covered with organic matter. 

The precipitation record spanning the M09 watershed premining period was 
from May 1, 1976, through January 19, 1977. The total precipitation for the 
period was 24.02 inches, with snowfall accounting for 2.93 inches. The most 
extreme event occurred on July 11, 1976, when rainfall amounted to 3.02 inches. 
The peak intensity of this event was 3.60 in/hr for 3 minutes — totaling 0.18 
inch. The frequency associated with the event was a 25-year, 3-hour event of 
2.73 inches. 

A spring was developed on the watershed at the outcrop of the No. 9 coal 
seam. The minimum flow rate of the spring was 0.0 cfs, and the maximum was 
0.214 cfs. The average daily springflow ranged from 0.0 to 0.0444 cfs. 

Mining commenced on the watershed before a full year's water quantity and 
quality data were obtained (data for the winter and early spring are missing) . 
The total flow for the period of record (6-8-76 to 1-19-77) was 12.44 inches, 
while the total precipitation for the same period was 20.21 inches. The peak 
runoff event occurred on July 11, 1976. The peak flow for the event was 81.95 
cfs with the causative precipitation being 3.02 inches. 

Base flow water had average concentrations of 46 yg/1 iron, 24 yg/1 
manganese, and 157 mg/1 suspended solids, and an average flow rate of 0.024 
cfs. Runoff water had average concentrations of 228 yg/1 iron, 92 yg/1 
manganese, and 1,110 mg/1 suspended solids, and an average flow rate of 2.711 
cfs. 

Three aquifer systems were measured in watershed M09. The ground-water 
divide for the top aquifer (above the clay that underlies the No. 9 coal) 
coincides with the surface drainage divide. Flow in the middle aquifer (above 
the clay that underlies the No. 8 coal) involves an unmeasured west-to-east 
underflow across the northern part of the watershed. This aquifer is part of 
a more extensive flow system which is away from the influence of the stream 
and is recharged and discharged mostly outside of the watershed. Potentiom- 
etric head in the northwest part of the middle aquifer is above the overlying 
clay, at least during part of the year, so that confined conditions exist. 
In the deep aquifer, water movement is northerly; the top of this saturated 
zone is about 70 feet below the middle aquifer. 



68 



Dissolved solids concentration of much of the water in the middle and 
deep aquifers exceeds the recommended 500 mg/1 limit. Chloride concentration 
in excessive (greater than 250 mg/1) in the eastern part of the middle aquifer 
and in the deep aquifer. Water in the top aquifer is very hard (greater than 
180 mg/1 hardness as CaC0 3 ). It is softer in parts of the deeper aquifers 
where sodium is the dominant cation. Dissolved iron exceeded the recommended 
limit (0.3 mg/1) in one sample, and dissolved manganese was excessive (greater 
than 0.05 mg/1) in several samples. The recommended limit for dissolved 
cyanide concentration (0.01 mg/1) was exceeded in two samples from the middle 
aquifer and two from the deep aquifer. 

Watershed Jll 

The premining condition of watershed Jll (fig. 4) is characterized by an 
ephemeral stream 1,400 feet long. The maximum elevation is 1,280 feet, and 
the minimum elevation is 1,135 feet. The watershed has an area of 29.1 acres, 
with a western aspect. 




200 



200 

i 



Scale, feet 



.EGEND 
istrument plot 

Core site 

/ell monitoring the 2nd aquifer 
Sediment pond 
Gaging standard 

/atershed boundary 
Intermittent streams 
Contour line 
Coal outcrop 
Access tube 



FIGURE 4. - Premining topographic map of watershed Jll showing instrumentation sites. 



69 



Four soil types, constituting 10 soil delineations, were mapped in the 
watershed. The soil mapping units are the Berks, Coshocton, Culleka, and 
Gilpin. Soil sampling has not been completed for this watershed. 

Much of the area is in pasture, both open and wooded. Only 4 of 11 
sample points are wooded, and average timber volumes are low. The dominant 
species are black cherry, ash, and ailanthus. Ground cover for the area is 
quite variable, including herbaceous vegetation ranging from 40 to 100 percent, 
woody vegetation to 9 percent, duff to 55 percent, and bare soil and/or 
rock to 14 percent. Average ground cover values for herbs, woody vegetation, 
duff, and bare soil are 87, 2, 10 and 1 percent, respectively. 

The precipitation record for the Jll watershed began on May 1, 1977. 
Since the watershed has not yet been mined, the report was arbitrarily cut 
off at December 31, 1977. The total precipitation for the period was 28.64 
inches. The most extreme event during the period occurred on July 21, 1976, 
when rainfall amounted to 1.93 inches. The peak intensity of this storm was 
7.5 in/hr for 2 minutes, totaling 0.25 inch. The frequency associated with 
the event was a 2-year, 3-hour event of 1.66 inches. 

The total surface flow for the period of record was 2.07 inches, while 
the total precipitation was 27.14 inches. The peak event occurred on 
July 21, 1977. The peak flow for the event was 6.31 cfs, with the causative 
precipitation being 1.93 inches. Base flow water had average concentrations 
of <3 yg/1 iron, 25 yg/1 manganese, and 44 mg/1 suspended solids, and an 
average flow rate of 0.042 cfs. The runoff water had average concentrations 
of 14 yg/1 iron, 54 yg/1 manganese, and 118 mg/1 suspended solids, and an 
average flow rate of 0.89 cfs. 

The top aquifer at the Jll site is above the shaly clay that underlies 
the No. 11 coal; the middle aquifer occurs above the shaly clay that underlies 
the No. 9 coal. Underflow does not appear significant in either aquifer. The 
top aquifer discharges to the surface as evapotranspiration and at one ungaged 
spring; the middle aquifer discharges as evapotranspiration and base flow. 
The two deepest wells penetrate mined-out openings in No. 8 coal and are 
dry; much of the No. 8 coal has been removed. More detailed description of 
the' Jll ground-water system will be undertaken as premining data collection 
continues. 

The top aquifer at Jll contains water of the calcium bicarbonate and 
calcium sulfate types. Samples collected from the middle aquifer were 
bicarbonate waters, and sodium and calcium were the dominant cations. The 
predominance of one major ion over another is not as extreme at Jll as at 
other study watersheds. 

Watershed J08 

The premining condition of watershed J08 Cfig- 5) is characterized by a 
continuously flowing stream 1,200 feet long. The maximum elevation of the 
watershed is 1,200 feet, and the minimum elevation is 880 feet. The watershed 
has an area of 51.8 acres, with a southern aspect. 



70 



6 



-200 



LEGEND 

Well monitoring the 2nd aquifer 
Gaging standard 

Watershed boundary 
Intermittent streams 
Contour line 
Coal outcrop 
Access tube 






-N- 




200 

_l 



Scale, feet 

FIGURE 5. - Premining topographic map of watershed J08 showing proposed and existing 
instrumentation sites. 

Four soil types, constituting 13 soil delineations, were mapped on the 
watershed. The soil mapping units are the Elba, Gilpin, Guernsey, and surface 
mine spoil. Soil sampling has not been completed for the watershed. 

On this watershed herbaceous vegetation cover ranges from 6 to 63 percent, 
woody cover from to 5 percent, duff from to 77 percent, and bare soil and 
rock from to 82 percent. The average cover values for herbs, woody vegeta- 
tion, duff, and bare soil and/or rock are 35, 4, 42, and 19 percent, respec- 
tively. The gross sawtimber volume is 389 board feet per acre, and the major 
species are black locust, black cherry, American elm, osage orange, and black 
walnut. Major poletimber species, representing a gross of 7.8 cords per acre, 
are black cherry, osage orange, black locust, and white ash. Woody 



71 



reproduction species include white ash, cherry, black locust, oak, osage 
orange, and elm. 

Weather data collected for the Jll site are being used for this site also. 
No surface water quality or quantity data are available, since measuring and 
sampling equipment is yet to be installed. 

Definition of the flow systems is not possible because only one well was 
completed in each aquifer. 

Analyses of ground water from J08 indicate calcium sulfate water in the 
top aquifer, sodium bicarbonate water in the middle aquifer, and sodium chlo- 
ride water in the deep aquifer. Water in the top aquifer is very hard and 
has dissolved-solids concentration exceeding the recommended limit of 500 mg/1 
and sulfate concentration exceeding the recommended limit of 250 mg/1. Water 
in the middle aquifer is much softer, but slightly brackish and contains chlo- 
ride concentrations exceeding the recommended limit of 250 mg/1. Water in the 
deep aquifer is highly brackish. 

Watershed A06 

Watershed A06 (fig. 6) is the control site and will not be mined. The 
watershed is characterized by a continuously flowing stream 1,750 feet long. 
The maximum elevation is 1,290 feet, and the minimum elevation is 1,008 feet. 
The watershed has an area of 43.6 acres, with a southern aspect. 

Four soil types, constituting 10 soil delineations, were mapped in the 
watershed. The soil mapping units are the Berks, Coshocton-Rayne complex, 
Dekalb, and Rayne. 

Vegetation is quite diverse, ranging from upland oak-hickory types to 
planted stands of white and red pine. Vegetation within the area is of a 
discontinuous cover form. Small areas within the watershed show recent 
interruptions. Ground cover is quite variable, including herbaceous vegeta- 
tion ranging from 2 to 56 percent, woody vegetation from 1 to 42 percent, and 
duff from 38 to 86 percent. The average cover values for herbs, wcody 
vegetation, duff, and bare soil and/or rock are 3, 16, 68, and 3 percent, 
respectively. The gross sawtimber volume is about 18,000 board feet per acre, 
and the major species are tulip poplar, red oak, white oak, red pine, and 
white pine. Poletimber gross volume is 27.0 cords per acre, and the major 
species include red pine, tulip poplar, and black locust. 

The precipitation record considered for this report covers the period from 
July 1, 1976, through December 31, 1977. The total precipitation for the 
period of record was 95.32 inches. The most extreme event occurred on 
July 11, 1976, when the rainfall amounted to 1.75 inches. The frequency 
associated with the event was a 5-year, 1-hour event of 1.61 inches. 

Springflow was measured from an existing developed spring on the Clarion 
clay, which comprises the second highest impermeable layer in the watershed. 
The minimum flow rate of the spring was 0.0003 cf s , and the maximum was 
0.0712 cfs. The average daily springflow ranged from 0.0003 to 0.444 cfs. 



72 



■1200 




-N- 



200 

I 



Scale.feet 



LEGEND 



Well monitoring the 2nd aquifer 
Gaging standard 

— Watershed boundary 
Contour line 

Coal outcrop 

Intermittent streams 

Access tube 
FIGURE 6. - Premining topographic map of watershed A06 showing instrumentation sites. 

The total surface water flow for the period was 33.95 inches. The peak 
runoff event occurred on July 11, 1976. The flow for the event was 13.80 cfs, 
with the causative precipitation being 1.75 inches. Base flow water had 
average concentrations of <22 yg/1 iron, 344 yg/1 manganese, and 45 mg/1 
suspended solids, and an average flow of 0.0098 cfs. The runoff water had 
average concentrations of 52 yg/1 iron, 64 yg/1 manganese, and 147 mg/1 sus- 
pended solids, and an average flow rate of 0.84 cfs. 

The top aquifer at the A06 site occurs above the clay that underlies the 
No. 6 coal, and the middle aquifer occurs above the clay that underlies the 
No. 4 coal. Surface loss from the top aquifer is mainly as evapotranspiration; 
that from the middle aquifer is evapotranspiration, base flow to the stream, 
and spring flow at spring gage. Underflow out of the watershed to the north- 
west occurs in both aquifers, although the top aquifer flow is from the divide 
toward the coal outcrop at times. In the deep aquifer water moves southward; 
the top of this saturated zone is about 20 feet below the middle aquifer. 



73 



Ground water in the top aquifer of the control watershed is of the calcium 
bicarbonate type. As in the other watersheds, water types in deeper aquifers 
are more diverse. In the middle aquifer, calcium, sodium, sulfate, or 
bicarbonate may each predominate. The deep aquifer contains sodium bicarbon- 
ate and sodium sulfate waters. Dissolved-solids concentration exceeded 500 
mg/1 in two samples from the middle aquifer and from both wells in the deep 
aquifer. Most water is hard to very hard. Recommended limits of concentra- 
tion for dissolved iron and manganese (0.3 and 0.05 mg/1, respectively) were 
commonly exceeded in all aquifers. Cyanide concentration exceeded 0.01 mg/1 
in one sample. 

SUMMARY 

Demand for coal will increase in the future. Demands for environmental 
safeguards will also grow, as evidenced by the passage of the Federal surface 
mining law and by various State enactments. 

Mines will be required to monitor ground water and to determine the 
hydrologic effects of mining, and regulatory agencies are required by law to 
determine the effects of mining by incorporating all of the hydrologic 
information gathered by mining companies. It is felt that this research 
program will be a first step in helping companies comply with the laws by 
establishing patterns for developing this information. 



74 



DRAGLINE CABLE REMOVAL PROJECT 

by 

G. Ken Derby 1 



INTRODUCTION 

During a routine visit by a Bureau of Mines representative to a surface 
coal mine using draglines for overburden removal, a drag cable broke. When 
inquiries were made about how repairs would be accomplished, the cannon method 
of socket and wedge separation was explained. During the discussion, the 
service personnel stated that they considered removing the cable in this way 
to be efficient but hazardous, and that they felt relieved when the task was 
completed without an accident or an injury. This concern was reiterated at 
other mines and in discussions with industry representatives. Upon further 
investigation, it was discovered that although socket and wedge separation 
is the predominant method of performing the task in the United States, it 
has been outlawed in Canada owing to its inherent hazards. 

The objectives of the project reported herein included gathering data to 
determine the level of force required to separate wedge and socket cable 
terminations of various sizes and makes of draglines, establishing the level 
of forces generated by the cannon method, and using the data compiled to 
improve or create new methods and equipment for cable removal. 

PRESENT SEPARATION METHODS 

Cable removal, specifically socket and wedge separation, is usually 
performed by one of three methods when the cable is attached to the drag 
bucket. In brief they are 

1. Explosive Impact. -Commonly referred to as the cannon method, this is 
the predominant method used in the United States. The main body of the device 
(fig. 1) used to hold and direct the charge and impeller is generally fabrica- 
ted from whatever type of steel material is available, in diameters ranging from 
14 to 16 inches by 32 to 36 inches long. The bore is governed by the width of 
the wedge being removed, which is generally in the range of 4 to 6 inches. 
The impeller is made of steel with a diameter 1/8 inch smaller than the bore 
and a length ranging from 12 to 20 inches. Explosive force is generated by 
either 40- or 50-grain primer cord. The length of charge is determined by 
trial-and-f ail method. A starting length of charge is decided upon and tried. 
If separation is not achieved, the length is increased in increments until 
separation is accomplished. Thereafter, the successful amount of charge is 
used unless a failure to affect separation occurs. In this event, the length 
of charge is again increased until separation occurs. This method, although 
considered hazardous, is highly effective. 

^Mechanical engineering technician, Spokane Research Center, Bureau of Mines, 
Spokane, Wash. 



75 




FIGURE 1. - Cable wedge removal cannon and impeller. In this version, the cannon is bored 
to 4-1/8 inches with a 4-inch-diameter impeller, 14 inches long. 

2. Manual Impact . -This method is now in general use in Canada and by some 
operators in the United States. Impact force is applied by use of a hand-held 
sledge hammer, or a pendulum ram suspended from a mobile crane. Because the 
degree of force required to effect separation increases in relation to the size 
of the dragline, use of hand-held sledge hammers is restricted to draglines 
under 40 yards in capacity. 

3. Burn Out. -This method is no longer in general use. It is accomplished 
by use of an extended oxyacetylene nozzle to flame-cut the cable wedged inside 
of the socket to relieve the pressure fit. 

PROJECT RESEARCH TO DATE 



Fabrication and Trials of Pendulum Impact Rams 

Present and past users of this type of device were surveyed to ascertain 
problems experienced and optimum weight needed to generate the required force. 
The largest ram we uncovered weighed 1,600 pounds and was used for removing the 
cables on 110-cubic-yard bucket draglines. We also learned that users had 



76 

experienced difficulty in holding the ram level for proper impact and problems 
with reverberation in the crane cable. Our present ram design (fig. 2) 
offsets the known problems. A chain, two-point connecting harness with a 15- 
foot leader was used. Chain material was chosen for flexibility and strength. 
The 15-foot leader enables cinching of the crane hook to the boom to reduce 
reverberation. The two-point hookup eliminates the effort required to main- 
tain the device on a level keel, permitting an even and maximum impact. To 
date, four rams have been fabricated in weights of 400, 800, 1,000, and 1,400 
pounds to accommodate the various sizes of draglines. 

Separation has been attempted on four separate occasions with two positive 
and two negative results. On each attempt, the two drag links were worked. 
The two successful attempts were on 60-cubic-yard machines using the 800-pound 
ram. One of the unsuccessful attempts was on a 60-cubic-yard machine that had 
previously yielded positive results, and the second was on a 78-cubic-yard 
machine. The 800- and 1,000-pound rams were tried on both occasions. Investi- 
gation to determine why separation was not attained produced the following 
results: 

1. On the 60-cubic-yard machine, a new type wedge and socket made from 
a softer material had been installed. This allowed the cable to cut deeper 
into both the wedge and socket, producing a tighter fit. Laboratory separation 
of the newer design units proved that a much higher force was required to 
effect separation than for the older design. The manufacturer confirmed that 
this aspect was not taken into consideration when the design change was made. 

2. The second negative attempt is believed to be our fault in not recog- 
nizing the need for firmly anchoring the socket during impact. Force was 
absorbed by movement of the unit. The operators of the second unit have agreed 
to supply us with joined units for laboratory separation testing. When we 
have determined the separation forces required, they will allow further 
attempts with the ram. 

Controlled Wedge and Socket Separation — Eight units have been separated 
to date using a Tinius Olsen, 400,000-psi testing machine (fig. 3). Six of 
the wedge and sockets were from the 60-cubic-yard machine with which we experi- 
enced the failure on the second ram attempt. We found that a wide range of 
force was required to effect separation. The first two units separated were 
of the older design and required 59,300 and 76,900 pounds of force. The force 
required for the four units of the newer design ranged from 93,000 to 132,200 
pounds. The remaining two units separated were from a different make of 
machine, but of the same size. Separation force required was much lower at 
31,250 and 45,250 pounds. 

Cannon Method Force Generation Determination — The Spokane Research Center 
fabricated a cannon to determine the degree of force generated using a typical 
cannon design with 40- and 50-grain primer cord as the explosive force. 
Instrumentation was a mix of specially designed and fabricated items with 
commercial products. Testing was designed to measure the force generated 
at detonation and the velocity of the impeller, which in turn can be converted 



77 




FIGURE 2. - Fourteen-thousand-pound pendulum impact ram. 



78 




FIGURE 3. - Wedge-and-socket controlled separation. Wedge-and-socket unit from a 60-cubic- 
yard machine mounted in a locally fabricated holder. The testing machine is a 
400,000-psi Tinius Olsen. 



79 




f 



FIGURE 4. - Cannon device instrumented for testing. 

to impact force (fig. 4). Preliminary testing was started but was halted 
before conclusive data could be compiled owing to failure of a commercial 
transducer used to measure the internal force. Testing will continue when 
the failure has been corrected. 

FUTURE PROJECT PLANS 

Research will continue to follow different avenues of approach to deter- 
mine (1) magnitude of forces required to effect separation of the socket and 
wedges of the various sizes and manufacture of dragline cable terminations, 

(2) magnitude of forces produced by the cannon and impact rams, and 

(3) improved methods and equipment for cable removal. 



Arrangements have been completed to obtain four more joined sockets from 
a 60-cubic-yard dragline and four from a 78-cubic-yard dragline. Preliminary 
discussions have also been conducted to obtain joined units from 110-cubic- 
yard draglines. When the complete range of data is compiled and analyzed, 



80 



it will provide a better, but not complete, understanding of the forces 
required for cable separation. Tests to date indicate that a wide range of 
forces may be needed within each size of dragline. Variations in design and 
strength of material of the socket and wedges, as well as length of time in 
use, affect the amount of force needed for removal. A complete understanding 
of the subject could be obtained only by controlled separation testing of all 
models of the various manufacturers of dragline equipment over the working 
life of the units. This is not possible under the limited time and funding 
allotted for this project. However, it is believed that sufficient data will 
be obtained to produce significant improvements in removal equipment design 
and procedural techniques. 

When complete data have been compiled as to the forces now generated by 
the cannon method, they will be presented to ballistic experts to determine 
the extent of present hazard, and if a less hazardous explosive charge and 
procedure can be devised. The data will also be used to help determine the 
forces needed to effect separation of various sizes and makes of draglines, 
and correlated with the forces generated by the different weights of impact 
rams to determine their capabilities. 

Other areas of equipment design will also be explored, such as portable 
hydraulic equipment designed for on-site use and improved cannon design. 



■frU.S. GOVERNMENT PRINTING OFFICE: 1980-603-102/38 int.-bu.of mines,pgh.,pa. 24621 






**%> 

■& 






•- ^** :1ft' ^^ 



v^' 




o°*.^>A .Av^-X .c *.-^:.^ „/// 
















* ^ 















^cr 




'bV 




' ^>. 4 ."„ 









'• A V ^ 
* A* "** 












4> . 




% 













*bV" 

























•5 



.' ^ 



^°^ 



.0' ^••- , <» v 











:. ^. 



'. ^0* 











^ 












'bJ-' 




^■o« .' 







^ v * 







V 









^ < 









r *.-XT- /V 



**b 











■^ 







. ^O A^ % 

*b# 













^°^ 










V^'S 



§^4*. ^ A* .. 

v*<t V " 









^, 4 






b.. ^TTT**^ 










jV 



'bV* 



* /\ '-siK-" ***** 









i0 V, 




•?5 ^*. 

V % »!••- cv a*> »i^L'» -?• 






» k> 

■-L'- O «■ - 




4?^, 




^0< 




A*> •i^Lf* ^ 



^ .^ «vi^ ^ a^ .: 



^^* :sm&~ ^c* v .* 






^-: 



' * A* ^ oVJIAF * 4? ^ • ®iiS » A^ 




^S 



V a 




i- ^ 




^bv* :£Mfa- "*W !«^iS : ; "bv* 






V * ' * ' 



^ 

c* 



A° 'UflL'* > 










^>» 4 



A O^ '^C^^F^ ' 



£°*- 




\ *o V* 










V "-.;". 












.-• % ++ 

















; j^v 




'bK 



^ 



A^°^ 




^ ^ 




<. '•••' A° 






■ • • r "\> 









»>* 



.0 












Wo <V -T" 









v*-.. 






6* O 










;• .«? ^ "-VW . * 



: A * V "V -. 




* o 













fi° * 






<v . « • < 



^ *. 




^0* 




° J* • 
iP-V 




c v »' 










4 o 






«T 




•A, 



> ^ \% 




O^ * c „ o ' 







TU a'* ♦ 








^ u ... 



■^ *, 



< o 



C v ♦* 














!- ^> 



u 

v 



•J- c ° " ' « <«>,. 



•* *6 




P*.^ 



^o< 






v**'-aK- ; x/'- 










^•^ 'infill; *f 




















•dfe".°° ^ .-^ii-%. G °-iife-> y.-^b-^ ^*Ma&°» /'^ 



4-°^ 




